Scale, simplified
Your drawing. Real life. Any scale.
5 m
≈ 16 ft 4.85 in
≈ 0 ft 1.97 in
Use custom scale when printing. Turn off fit to page.
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Architectural scale calculator: from drawing to real life
This free architectural scale calculator converts a length on a drawing or model into its real-life size and its size at another scale. Use it for floor plans, sections, elevations, site plans and physical models. Results appear instantly in centimetres and feet and inches, with metres shown for the real-life size.
How to use the scale calculator
- Choose your current scale in From scale, such as 1:50.
- Enter the length you measured on your drawing or model, then choose its unit.
- Choose your new scale in To scale. Read the real-life size, the new drawing size and the print percentage below.
A quick example
A wall measures 10 cm on a 1:50 floor plan. In real life, it is 500 cm, or 5 m, long: approximately 16 ft 4.85 in. At 1:100, that same wall measures 5 cm on the page. To resize the original drawing, print it at 50%.
Common drawing scale conversions
For a length measuring 10 cm on your original drawing:
| From scale | To scale | New length | Print at |
|---|---|---|---|
| 1:50 | 1:100 | 5 cm | 50% |
| 1:100 | 1:50 | 20 cm | 200% |
| 1:100 | 1:200 | 5 cm | 50% |
| 1:200 | 1:100 | 20 cm | 200% |
The simple maths behind it
Real-life length = measured length × current scale number.
New drawing length = measured length × current scale number ÷ new scale number.
Print percentage = current scale number ÷ new scale number × 100.
The scale number is the number after the colon: 50 in 1:50. Use the same unit throughout a calculation. The calculator handles the unit conversions for you.
A few useful things to know
What does a scale of 1:50 mean?
One unit on the drawing represents 50 of the same units in real life. So 1 cm on a 1:50 drawing equals 50 cm in real life. At 1:100, 1 cm equals 1 m. A larger scale number makes the drawing smaller.
Can I start with a real-life measurement?
Yes. Choose 1:1 in From scale, enter the real-life length and select your target scale. For example, 5 m in real life becomes 10 cm at 1:50 or 5 cm at 1:100.
Can I use millimetres, centimetres, metres, feet and inches?
Yes. Choose mm, cm, m, inches or feet for your input. The results show metric and imperial equivalents. Enter inches or decimal feet as one number; for example, 5 ft 6 in is 66 inches or 5.5 feet. Inches in the results are rounded to two decimal places.
How do I keep a printed plan at the right scale?
Start with a drawing that is already at its stated scale. Use the calculated custom print percentage and turn off fit to page. Keep width and height linked when resizing. Changing the paper size or screen zoom does not establish a reliable drawing scale. Check a known dimension with a ruler after printing.
Does this work for a 3D model or a perspective rendering?
For a physical model, use a measured length and the model scale. In CAD or BIM, geometry is usually drawn at 1:1, so change the viewport or print scale when preparing a sheet. A perspective rendering has no single scale across the image, so this calculator cannot recover dimensions from it.