CAD Unit & Drawing Scale Converter
Convert mm/cm/in/pt units and calculate drawing scale ratios · free, no signup
See CAD Unit & Drawing Scale Converter in action
Free CAD Unit & Drawing Scale Converter
CAD and drafting work constantly crosses between units — millimeters in a 3D model, inches on a print, points in a layout, or a scaled drawing that represents a much larger real object. The unit converter handles the everyday conversions: millimeters, centimeters, meters, inches, feet, points and pixels (at both 96 and 300 DPI), all computed precisely rather than with rounded rule-of-thumb figures.
The scale calculator solves the other common CAD problem: given a real-world measurement and a drawing scale ratio such as 1:50 or 1:100 (or a custom ratio), it computes the exact size that measurement should be drawn at — and works in reverse too, turning a measured drawing length back into the real-world size it represents.
Key features
Seven common CAD/drafting units
Millimeters, centimeters, meters, inches, feet, points and pixels, with precise conversion factors.
Screen pixels at 96 and 300 DPI
Converts real-world size to on-screen or print pixel dimensions correctly.
Drawing scale calculator
Common architectural/engineering ratios (1:20 to 1:1000) or a custom ratio, in either direction.
Exact, not rounded
Every conversion uses precise factors rather than common rounded approximations.
How to use it
- Enter a value and choose the unit you're converting from and to.
- Read the converted value instantly.
- For scale work, enter a real-world or drawing length and choose a scale ratio.
- Switch direction (real-to-drawing or drawing-to-real) to solve either way.
Worked example
Example
A wall measuring 4.5 m in real life, drawn at 1:100 scale, should be drawn at 45 mm on paper. Converting that same 45mm drawing measurement back at 1:100 gives the real 4.5m wall length again.
Who uses this tool
Architects and engineers checking a scaled drawing
Verify a printed or digital drawing matches its stated scale.
CAD users moving between metric and imperial models
Convert dimensions precisely instead of rounding by hand.
Anyone preparing a print or export at a specific DPI
Convert real-world size into the correct pixel dimensions for 96 or 300 DPI output.
Tips for the best results
- Architectural scales are often written as a fraction (like 1/4" = 1'-0", which is the same ratio as 1:48) — if your drawing uses a fractional scale notation, convert it to a plain ratio first using that equivalence.
- For print output, 300 DPI is the standard minimum for sharp printed detail, while 96 DPI matches typical on-screen/web pixel density — pick the one matching your actual output target.
- When checking an existing drawing's scale, measure a known real-world dimension on the drawing and divide to find the actual ratio, rather than trusting a label that may not match the final print size if it was resized.
Common mistakes to avoid
- Assuming a drawing viewed on screen is 'to scale' without checking — screen zoom level changes the apparent size, so only a printed (or explicitly scaled digital) drawing has a fixed, meaningful scale.
- Mixing metric and imperial scale ratios without converting — a ratio like 1:50 behaves identically regardless of unit, but reading it against the wrong unit system gives a wrong real-world size.
- Forgetting that a larger scale denominator means a smaller drawing (1:1000 draws things much smaller than 1:50) — it's easy to invert this intuitively.
Why use AZRS QuickFix?
It is 100% free, needs no signup and has no watermark or usage limits. The tool runs in your browser, so what you type stays on your device, and it works on phones, tablets and desktops. New tools are added every week — bookmark this page or browse the full QuickFix toolbox.
Frequently asked questions
How do I convert millimeters to inches?
Divide by 25.4 — this tool does it precisely to avoid rounding error across repeated conversions.
What does a 1:100 scale mean?
Every 1 unit on the drawing represents 100 of that same unit in real life — so 1mm on the drawing equals 100mm (10cm) in reality.
How do I convert a fractional architectural scale like 1/4" = 1'-0"?
That's equivalent to a ratio of 1:48 — enter 48 as a custom scale ratio to use it in the calculator.
What DPI should I use for print output?
300 DPI is the standard for sharp printed detail; 96 DPI matches typical on-screen pixel density.
Is my data saved anywhere?
No, all figures are entered and calculated locally in your browser.