Best CAD Scale Calculator
Find the largest common metric, architectural or engineering scale that fits your drawing extents inside a selected CAD paper size and margin.
Enter your values, then select Calculate.
Runs in your browser. No calculation data is sent to an external service.
What this calculator does
The tool first calculates the exact minimum ratio required to fit both width and height. It then chooses the smallest standard denominator that is equal to or greater than that requirement—the largest common scale that still fits.
Example
An 80 m × 50 m drawing inside an A1 landscape sheet with 10 mm margins requires about 1:97.4. The next common metric scale is 1:100.
How to use the result
- Use Auto orientation when you want the tool to compare portrait and landscape.
- The result is a geometric fit; leave room for annotation and title-block content.
- The next smaller/safer scale can be a better production choice for crowded sheets.
Frequently asked questions
Why does the calculator choose 1:100 instead of 1:97.4?
Because 1:97.4 is the exact fit requirement, while 1:100 is the next common metric scale that fits.
Does a smaller denominator mean a larger drawing on paper?
Yes. 1:50 plots larger than 1:100.
Can I search architectural and engineering scales too?
Yes. Select the scale family or choose All common scales.
Explore more in CAD Plotting Tools & Calculators.