Scale Calculator
Scale calculator works out Scale factor and Scale as a ratio from Original length, New (scaled) length and Length measured on the drawing. The default figures on this page give scale factor of 2; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
4 steps
- Scale factor k = new ÷ original = 4 ÷ 2 = 2.
- Lengths scale by k, so this is a enlargement.
- Areas scale by k² = 4 and volumes by k³ = 8.
- Drawing scale 1 : 100: real = drawing × 100 ÷ 1 = 5 × 100 ÷ 1 = 500.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
What the scale calculator calculates
Finds the scale factor between an original and a scaled length, with the matching area and volume factors, and converts a drawing measurement to its real length using the drawing scale ratio.
How to use this scale calculator
Enter Original length, New (scaled) length, Length measured on the drawing and Drawing scale — drawing side. Scale factor updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Scale factor, Scale as a ratio and Enlargement or reduction.
The method follows OpenStax, Elementary Algebra 2e, section 9.6 and chapter 3: ratios, proportions and geometry applications and ISO 5455:1979, Technical drawings — Scales (designation of a scale as a ratio of drawing size to real size).
Doubling: original 2, new 4 example
With Original length: 2, New (scaled) length: 4, the calculator returns Scale factor: 2, Area scales by: 4, Volume scales by: 8. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Scale factor, Scale as a ratio and Enlargement or reduction. The inputs you can vary are Original length, New (scaled) length, Length measured on the drawing, Drawing scale — drawing side and Drawing scale — real side.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How to convert 1/100 to 1/50 scale?
Finds the scale factor between an original and a scaled length, with the matching area and volume factors, and converts a drawing measurement to its real length using the drawing scale ratio. Open “How this is worked out” beside the result to see each step for your own figures.
How do I convert 3/32 scale to 1/8 scale?
It needs Original length, New (scaled) length, Length measured on the drawing, Drawing scale — drawing side and Drawing scale — real side. Nothing else is required, and the figures stay in your browser.
How big is a 1:100 scale in inches?
The result gives Scale factor, Scale as a ratio, Enlargement or reduction, Area scales by, Volume scales by and Real length from the drawing, each labelled with its unit so the figure can be read on its own.
How do I convert measurements to 1:12 scale?
The page opens with worked default figures: scale factor of 2. Replace them with your own and every figure updates as you type.
What information do I need for the scale calculator?
You need Original length, New (scaled) length, Length measured on the drawing, Drawing scale — drawing side and Drawing scale — real side. The page opens with default figures that give scale factor of 2, so you can see the scale before entering your own.
What does this scale calculator show?
It shows Scale factor, Scale as a ratio, Enlargement or reduction, Area scales by, Volume scales by, Real length from the drawing, Drawing scale and Scale factor the other way, with the working and any warnings for your entries.