What is this application? This is a free, web-based reference toolkit built for AutoCAD drafters — beginners and veterans alike.
It covers everything related to scaling and units: the numbers that control how your drawing translates from screen to paper.
The app has 5 tools, each focused on a specific part of the workflow. You never have to do the math in your head — just look it up, type it in, and move on.
Use the navigation bar at the top of any page to jump between tools.
🗺 Part 1 — Navigating the App (5 Tools)
The navy bar just below the page header appears on every page. Click any link to switch tools instantly. The currently active page is highlighted in orange.
- 📐 Reference Card (this page) — A dense, one-page cheat sheet with every scale factor, conversion, formula, and system variable you use daily. The fastest lookup in the app.
- 🔢 Scale Calculator — Type or select a scale and instantly get your Scale Factor, Viewport XP Zoom, LTSCALE, DIMSCALE, and a full text-height table. One-click copy buttons let you paste values straight into AutoCAD.
- ⇄ Unit Converter — Live two-way converter between millimeters, centimeters, meters, decimal inches, feet-inches, and decimal feet. Also shows the nearest standard fractions (to the nearest 1/64") as you type.
- ½ Fraction Chart — Every 1/64" increment from 1/64" to 12" with its decimal-inch and millimeter equivalents. Color-coded by fraction type. Jump buttons skip you straight to any inch. Searchable.
- 📄 Title Block Setup — Step-by-step instructions for setting up Paper Space layouts, configuring the Page Setup Manager, setting up the DWG To PDF plotter, and sizing viewports correctly for all disciplines and sheet sizes.
On a phone or tablet? The nav bar wraps to two lines on smaller screens — scroll it left/right if a link seems cut off. Every page is touch-friendly.
📐 Part 2 — Quick Reference Card (This Page)
The Reference Card is laid out in four columns. Think of it as four mini-tables side by side. You scan left to right within a section to get all the numbers for one situation.
Column 1 — Unit Conventions
What it is: Before you draw a single line in AutoCAD, the software needs to know what one "drawing unit" represents in the real world. This table tells you the industry standard for each type of work.
How to read it: Find your discipline in the first column. The middle column tells you what 1 drawing unit equals on your screen. The third column tells you the display format AutoCAD will use.
Example: You're drawing a floor plan for a house.
→ Discipline = Architectural
→ 1 drawing unit = 1 inch
→ When you type "12", AutoCAD treats that as 12 inches (= 1 foot)
→ It will display as 1'-0" on screen
Beginner mistake to avoid: If you receive a drawing from an engineer using Civil units, their "100" means 100 feet. In your Architectural drawing, "100" means 100 inches. Always confirm which unit system a file uses before inserting it.
INSUNITS Values
What it is: INSUNITS is a setting in AutoCAD that tells the program what unit system your drawing uses. When you insert (bring in) another drawing or block, AutoCAD uses this number to automatically scale it to fit correctly.
How to set it: Type INSUNITS at the AutoCAD command line, press Enter, then type the number from the table that matches your drawing type.
You're working in an inch-based architectural drawing.
→ Type: INSUNITS → Enter → Type: 1 → Enter
Now if you insert a metric block (set to mm = 4),
AutoCAD automatically scales it by 1/25.4 so it fits correctly.
Rule of thumb: Set INSUNITS at the very start of every new drawing, before you draw or insert anything. Changing it later won't rescale existing geometry.
Metric ↔ Imperial Conversions
What it is: A simple lookup table for converting between the two major unit systems used in drafting worldwide — metric (millimeters, meters) and imperial (inches, feet).
How to read it: Find the row where the left column matches what you're converting FROM → TO. Multiply your number by the value in the right column to get the answer.
You have a steel beam that is 6 inches long.
You need to know how long it is in millimeters.
→ Row: "in → mm" → Multiply by: 25.4
→ 6 × 25.4 = 152.4 mm
You received a metric part that is 300 mm wide.
You need it in inches.
→ Row: "mm → in" → Multiply by: 0.039370
→ 300 × 0.039370 = 11.81 inches
The one number to memorize: 1 inch = 25.4 mm. This is exact, by international definition. Every other conversion in the table is derived from it.
Imperial Format Comparison
What it is: Two of AutoCAD's unit types — Architectural and Engineering — both use inches as their base unit, but they display the same distance differently. This table shows you how the same measurement looks in each format so you're never confused by a dimension.
How to read it: Pick any value in the first column. The second column shows how Architectural units would display it (feet, inches, fractions). The third shows how Engineering units display it (feet, decimal inches).
18 drawing units stored internally:
→ Architectural shows: 1'-6" (1 foot, 6 inches)
→ Engineering shows: 1'-6.0000" (1 foot, 6.0 decimal inches)
Both represent exactly the same physical distance — just formatted differently.
Column 2 — Architectural Scale Factors
What it is: This is the most-used table on the page if you do architectural or building drawings. It gives you every number you need for each standard drawing scale, pre-calculated.
How to read the columns:
- Drawing Scale — The scale shown on your title block (e.g., 1/4" = 1'-0" means 1/4 inch on paper = 1 foot in real life)
- SF (Scale Factor) — The core multiplier. Everything else is calculated from this one number.
- VP XP Zoom — The number you type when setting a viewport scale in Paper Space (e.g., type
1/48xp for 1/4" = 1'-0")
- LTSCALE — Set this equal to the SF. Controls how dashed/hidden lines look — if this is wrong, your dashes will be invisible or huge.
- Txt 1/8" — If you want your text to print at 1/8" tall, draw it at this height in Model Space
You're drawing a floor plan at 1/4" = 1'-0" scale.
→ Find row: 1/4" = 1'-0"
→ SF = 48
→ In Paper Space, zoom viewport to: 1/48xp
→ Set LTSCALE to: 48
→ Set DIMSCALE to: 48
→ Draw text at: 6.0" tall in Model Space (will plot at 1/8")
Highlighted rows (in blue) are the most commonly used scales in practice.
Column 3 — Civil / Engineering & Metric Scale Factors
Civil / Engineering Scales — What it is: Civil engineering drawings (roads, utilities, sites, surveys) cover large areas, so they use much smaller scales. Instead of "1/4 inch = 1 foot," civil drawings use "1 inch = 50 feet" or larger. In civil drawings, 1 drawing unit typically equals 1 foot (not 1 inch).
How to read it: Same as the Architectural table — find your scale, read across for SF, VP Zoom, and LTSCALE.
Civil site plan at 1" = 50' scale (1 unit = 1 foot):
→ SF = 50
→ VP Zoom: 1/50xp
→ LTSCALE = 50
Note: If your drawing uses 1 unit = 1 inch instead,
the SF becomes 50 × 12 = 600 (see the formula box below the table)
Metric Scales — What it is: Metric drawings use a simple ratio like 1:100, meaning 1 mm on paper = 100 mm in real life. The math is much simpler — the Scale Factor is just the second number of the ratio.
Metric floor plan at 1:100 scale:
→ SF = 100
→ VP Zoom: 1/100xp
→ LTSCALE = 100
→ DIMSCALE = 100
Column 4 — Master Formulas
What it is: The six formulas that control everything about scaling in AutoCAD. If you understand these, you can figure out any scale setting for any drawing without a lookup table.
Breaking down each formula:
- Scale Factor = Real size ÷ Drawing size — How many drawing units fit inside one real-world unit at your chosen scale
- VP Zoom XP = 1 ÷ Scale Factor — The number you type after the zoom command in a Paper Space viewport. This locks your view to the exact drawing scale.
- Model Text Height = Plotted Height × Scale Factor — Text drawn in Model Space needs to be drawn BIG so it prints small. Multiply your desired print size by the SF to get the draw height.
- LTSCALE = Scale Factor — One command, one number. Set it and your dashed lines will look correct at your drawing scale.
- DIMSCALE = Scale Factor — Same idea for dimension arrows, tick marks, and text inside dimensions.
- mm → in import = × 0.03937 — When you bring a metric file into an inch drawing, scale it by this number (= 1 ÷ 25.4) to correct the size.
Think of Scale Factor as the master key: Once you know it, you can derive every other number on this page. LTSCALE = SF. DIMSCALE = SF. VP Zoom = 1/SF. Text height = desired print height × SF.
Model Space Text Height Table
What it is: A pre-calculated lookup so you never have to do the text height math manually. Find the size you want text to print, find your scale factor column, and that's the height to draw your text in Model Space.
How to read it: Pick the plotted height you want (left column). Find your SF column. The cell value is what you type for text height in AutoCAD.
You want notes to print at 1/8" tall.
Your drawing scale is 1/4" = 1'-0" (SF = 48).
→ Row: 1/8" (0.125) Column: SF=48 → Answer: 6.00"
→ Set your text height to 6 inches in Model Space.
It will plot at exactly 1/8" on the printed sheet.
Standard Sheet Sizes
What it is: The standard paper sizes used for engineering and architectural drawings in both imperial (ANSI, Arch) and metric (ISO) systems.
How to use it: When you set up a Paper Space layout in AutoCAD, set the page size to match one of these standard sizes. Choose your sheet based on how much content you need to fit and what scale you're working at.
- ANSI A / B — Small detail sheets, letter/tabloid size, desktop printer friendly
- ANSI D / Arch D (24×36) — The most common size for residential drawings
- Arch E (36×48) — Large commercial projects, site plans
- ISO A1 / A0 — Metric equivalent of Arch D / Arch E
Viewport Scale Setup — Step by Step
What it is: The 7-step process to go from Model Space geometry to a properly scaled drawing on a printable layout sheet. This is the core workflow of professional CAD production.
- Step 1 — Draw at 1:1. Always draw at real-world size in Model Space. A 30-foot wall is drawn 30 feet long (360 units if 1 unit = 1 inch). No exceptions.
- Step 2 — Create a Layout. Click a Layout tab at the bottom of the screen. This is Paper Space — your virtual sheet of paper.
- Step 3 — Create a Viewport. Type MVIEW and draw a rectangle. This creates a "window" from Paper Space looking into Model Space.
- Step 4 — Activate the Viewport. Double-click inside the rectangle. You're now temporarily inside Model Space through the viewport.
- Step 5 — Set the zoom scale. Type Z (zoom), press Enter, then type your VP XP value from the table (e.g.,
1/48xp for 1/4" = 1'-0"). Press Enter.
- Step 6 — Lock the viewport. Double-click outside the viewport to return to Paper Space. Click the viewport border. Type VPLOCK, Enter, ON, Enter. This prevents accidental zoom changes.
- Step 7 — Plot at 1:1. In the Plot dialog, always set plot scale to 1:1. Your viewport is already handling the drawing scale.
Most common beginner error: Accidentally scrolling the mouse wheel inside an unlocked viewport and changing the scale without knowing it. Always lock your viewports immediately after setting the scale.
System Variables Quick Reference
What it is: AutoCAD stores its settings as named variables. This table shows the eight most important ones for scaling. Type any of these at the command line to check or change their value.
- UNITS — Opens the Drawing Units dialog. Start here on every new drawing. Shortcut: type UN.
- INSUNITS — Controls auto-scaling when inserting blocks or XREFs. Set once per drawing (see the INSUNITS table in Column 1).
- MEASUREMENT — Set to 0 for imperial, 1 for metric. Affects which linetype and hatch pattern library AutoCAD uses.
- LTSCALE — Linetype scale. Set equal to your Scale Factor. If your hidden lines look like solid lines or have invisible dashes, this is the culprit.
- PSLTSCALE — Keep this at 1 (default). It makes viewport linetypes automatically adjust to the viewport scale so you don't have to recalculate LTSCALE for each viewport.
- DIMSCALE — Makes dimension arrowheads, gaps, and text scale up so they're readable at your drawing scale. Set equal to your Scale Factor for non-annotative dimensions.
- CANNOSCALE — The active annotation scale. If you're using annotative text and dimensions (recommended for new drawings), make sure this matches your viewport scale.
- HPSCALE — Hatch pattern scale. Set equal to your Scale Factor so hatching (brick, concrete, insulation, etc.) looks correct at your drawing scale.
The Five Core Rules
Every experienced drafter follows these automatically. If something looks wrong in your drawing, run through this list and you will find the problem.
- Rule 1 — Draw at 1:1 in Model Space. Always. Real-world size, no scaling, no exceptions. A 30-foot wall is drawn 360 units long (if 1 unit = 1 inch). Scaling is handled entirely by the viewport — not in your geometry.
- Rule 2 — Set INSUNITS and UNITS before anything else. Get your unit system locked in before you draw or insert a single object. Changing it later won't rescale geometry that's already in the drawing.
- Rule 3 — Scale Factor drives everything. One number — SF — controls your LTSCALE, DIMSCALE, text height, and viewport XP zoom. Find it in the Scale Calculator, write it down, apply it everywhere.
- Rule 4 — Lock viewports after setting scale. An unlocked viewport can be accidentally scrolled, silently breaking your plot scale without you noticing until print time. Lock every viewport immediately after setting it.
- Rule 5 — Convert all units to one master before mixing. If you are working with files from different disciplines or different countries, pick one unit system and convert everything into it before your project starts. Use the Unit Converter tool to do the math.
Quick diagnostic: Use the DIST command to measure a known real-world dimension in your drawing. If AutoCAD's number doesn't match reality, you have a unit or scale mismatch. Go back to INSUNITS and UNITS to fix it.
🔢 Part 3 — Scale Calculator
What it does: You pick a discipline and a scale — the calculator instantly gives you every number you need for that scale in one place. No math required.
How to use it:
- Step 1 — Choose your discipline from the dropdown: Architectural, Engineering, Civil, Metric, or Decimal. This loads the correct list of standard scales for that type of work.
- Step 2 — Pick a scale from the second dropdown (e.g., 1/4" = 1' for an architectural floor plan).
- Or enter a custom Scale Factor directly if you already know it — type any number into the Custom SF field.
- Step 3 — Click Calculate. The results panel on the right fills in automatically.
What the results mean:
- Scale Factor (SF) — The master multiplier for your scale. Everything else flows from this number. For 1/4" = 1' the SF is 48.
- VP XP Zoom — The exact value to type when setting a viewport scale in Paper Space. For SF=48 you type
1/48xp in the AutoCAD zoom command.
- LTSCALE — Set this system variable to your SF. It controls how dashed and hidden lines look. Wrong LTSCALE = invisible dashes or enormous gaps.
- DIMSCALE — Set this to your SF too. It scales dimension arrowheads, text, and gaps so they look correct at your drawing scale.
- PSLTSCALE note — Set PSLTSCALE to 0 in Paper Space layouts to prevent linetypes from being scaled twice.
- Text Heights table — Shows the model-space height to draw text at for every common plotted size. Starred rows (★) are the most commonly used plotted text sizes. The Arch Display column converts the model height to feet-inches for architectural disciplines.
You're setting up an architectural floor plan at 1/4" = 1'-0".
→ Discipline: Architectural → Scale: 1/4" = 1'
→ SF = 48 → VP XP Zoom = 1/48xp → LTSCALE = 48 → DIMSCALE = 48
→ For 3/32" plotted text: draw it at 4.500" tall in Model Space
Copy buttons: Each result card has a small Copy button in the top-right corner. Click it to copy the value to your clipboard — then paste directly into AutoCAD's command line.
⇄ Part 4 — Unit Converter
What it does: Converts any measurement between every unit format used in drafting — metric and imperial — in real time as you type. This is the tool to use when you receive a drawing in one unit system and need to work in another.
How to use it: There are two input panels — Metric on the left, Imperial on the right. Type a value into any field and all other fields update instantly.
- Millimeters, Centimeters, Meters — Type in the metric panel. All imperial fields update at once.
- Decimal Inches — Type a decimal like 3.5 and see mm, feet-inches, and decimal feet automatically.
- Feet & Inches — Two separate fields: whole feet in the left box, inches (can be decimal) in the right. AutoCAD architectural format.
- Decimal Feet — Common in civil/survey drawings where 1 unit = 1 foot. Type 2.5 to see 2 feet 6 inches and its metric equivalent.
Nearest Fraction Finder: The orange panel below the inputs shows the nearest standard fractions to whatever decimal value you've entered. The closest fractions in 1/64", 1/32", 1/16", 1/8", and 1/4" increments are all displayed. A green ✓ exact label appears when the decimal is a perfect fraction.
You receive a metric dimension of 152.4 mm from a vendor.
→ Type 152.4 in the Millimeters field
→ Instantly see: 6.000" decimal inches | 0'-6" feet-inches | 0.500 decimal feet
→ Fraction finder shows: 6" (exact ✓)
You need to convert 2'-6 3/4" into millimeters for a metric submittal.
→ Type 2 in the Feet field and 6.75 in the Inches field
→ Instantly see: 774.700 mm | 30.500" decimal inches | 2.542 decimal feet
Quick Reference Table: Scroll down on the converter page for a built-in table of common reference conversions — standard sheet sizes, metric benchmarks, and imperial benchmarks all pre-calculated.
½ Part 5 — Fraction Chart
What it covers: Every 1/64-inch increment from 1/64" all the way to 12 inches — 768 rows total — with the exact decimal-inch and millimeter value for each one. This is the table machinists, fabricators, and detailers use constantly when translating between a fraction on a print and a decimal on a digital readout (or vice versa).
Color coding — what each color means:
- Dark Navy — Whole inches (1", 2", 3"… 12"). These are major section dividers.
- Orange — Half-inch marks (1/2", 1-1/2", 2-1/2"…). Second most prominent.
- Dark Blue — Quarter-inch marks (1/4", 3/4", 1-1/4"…).
- Medium Blue — Eighth-inch marks (1/8", 3/8", 5/8"…).
- Light Blue — Sixteenth-inch marks.
- Pale Blue — Thirty-second-inch marks.
- White — Sixty-fourth-inch marks (the finest increment).
Jump navigation: The row of numbered buttons (1" through 12") below the search bar scroll the page directly to that whole-inch section. Click 6" to jump instantly to the 6-inch section without scrolling through hundreds of rows.
Search: Type any value in the search box — a fraction like 3-1/4, a decimal like .375, or a millimeter value like 9.525 — and the table filters to matching rows only. The result count updates live.
You have a bolt hole at 17/32" on a drawing and need the millimeter equivalent for a metric drill bit.
→ Type 17/32 in the search box
→ Instantly shows: 17/32" = 0.531" = 13.494 mm
Printing the chart: Use your browser's Print function (Ctrl/Cmd+P). The navigation bar and search box are automatically hidden when printing, leaving just the clean table. The color coding is preserved on color printers.
📄 Part 6 — Title Block & Layout Setup
What it covers: The complete workflow for setting up a professional, print-ready AutoCAD layout. This is where Paper Space, the Page Setup Manager, PDF plotting, and sheet sizes all come together. If the Reference Card tells you what your scale numbers are, the Title Block page tells you where to put them.
The 8 sections on that page:
- Paper Space Fundamentals — The difference between Model Space (where you draw) and Paper Space (where you compose your sheet for printing). Everything drawn in Model Space appears in Paper Space through a viewport window.
- Page Setup Manager — Step by Step — How to open and configure the Page Setup Manager dialog. This is where you assign a plotter, paper size, plot style, and plot scale to a layout. Set it once per layout and it sticks.
- DWG To PDF Plotter Setup — How to configure AutoCAD's built-in PDF creator (DWG To PDF.pc3) so you can plot directly to a PDF file without buying third-party software. Covers paper size selection and orientation.
- Sheet Size Reference Tables — All standard sheet sizes for ANSI (engineering), Arch (architectural), and ISO (metric) formats with exact dimensions in both inches and millimeters. Use these when setting your Page Setup paper size.
- Layout Setup by Discipline — Viewport extents and recommended scales for architectural, civil/engineering, metric, and decimal drawings on each standard sheet size. Tells you which scale to use for which sheet so your drawing fits correctly.
- Complete Layout Workflow — The full 10-step process from creating a new layout to locking your viewport and plotting. Follow this checklist for every new sheet you set up.
- Plot Styles — CTB vs STB — Explains the difference between Color-Dependent plot styles (CTB, older method) and Named plot styles (STB, newer method). CTB maps AutoCAD colors to line weights; STB assigns styles directly to objects. Most firms still use CTB.
- Troubleshooting — A table of the most common layout and plotting problems with their causes and fixes. If your drawing plots at the wrong size, linetypes look wrong in Paper Space, or your PDF comes out blank — the answer is in this table.
Setting up a D-size (24"×36") architectural sheet at 1/4" = 1'-0":
→ Title Block page → Sheet Size Tables → ANSI D = 34"×22" or Arch D = 36"×24"
→ Page Setup: Paper = ARCH D (36.00×24.00 inches), Plotter = DWG To PDF.pc3, Scale = 1:1
→ Scale Calculator: SF for 1/4"=1' = 48
→ Viewport zoom: type 1/48xp → Lock viewport → Plot at 1:1
The golden rule of layouts: Always plot at 1:1 from Paper Space. Your viewport handles the drawing scale. If you try to scale the plot itself, everything doubles up and you get the wrong size.
🖨 Part 7 — Printing & Mobile Use
Printing any page: Press Ctrl+P (Windows) or Cmd+P (Mac) on any page in this app. The dark navigation bar, search box, and buttons are automatically hidden for printing, leaving a clean, ink-friendly version of the content. Color-coded rows are preserved on color printers.
Mobile and tablet: Every page in this app is responsive — it adjusts its layout for smaller screens automatically. The four-column Reference Card collapses to two columns on tablets and one column on phones. Tables become horizontally scrollable if they're too wide for the screen. The navigation bar wraps to fit.
Downloading the PDF Reference Card: Click the orange Download PDF button in the header of the Reference Card page to save a compact one-page version to your device. This is handy for posting at your desk or using offline.
Bookmark this app: Add it to your browser bookmarks or home screen (on mobile, use "Add to Home Screen" in your browser menu) for instant access during a project without having to search for it.
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