Model Scale Converter

Choose scale denominators or corresponding source and target dimensions. A linear factor k gives area factor k² and volume factor k³ only for geometrically similar shapes, including similar cones. Changing units reinterprets the numbers.

The scale bar is exported at its specified paper length, between 10 and 250 mm. Its labels show real-world lengths at the target scale in the selected unit. Print at 100% and verify the bar with a ruler. A 1 cm printed bar at 1:100 represents 1 metre.

For an enlargement of 10:1, enter 0.1 as the target denominator in the 1:N convention. Converting from 1:10 to 1:20 halves every corresponding length.

How to use it: enter a dimension you know and the scale it's at (use 1 for a real, full-size measurement), then the scale you want to convert to. This covers three cases: real size → model size, model size → real size (set target scale to 1), and model scale → a different model scale, all with the same calculation.

Formula. A dimension at 1:N is real size divided by N. Converting between two scales is just the ratio of the two N values:

Target dimension = known dimension × (known scale N ÷ target scale N)

The same ratio, as a percentage, is exactly the number to type into 3D-printing slicer software to resize a model from the known scale to the target scale: Slicer resize % = (known scale N ÷ target scale N) × 100.

Worked example. A real car is 1770 mm long (known scale 1). At 1:24 scale: target dimension = 1770 × (1 ÷ 24) = 73.75 mm; slicer resize = (1 ÷ 24) × 100 ≈ 4.17%. Converting a 50 mm part from 1:48 to 1:35 instead: target = 50 × (48 ÷ 35) ≈ 68.57 mm; slicer resize = (48 ÷ 35) × 100 ≈ 137.14% - scale the 1:48 file up by that percentage to get the 1:35 equivalent.

The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.

Known measurements

Source and target scales

Length unit

mm

Known dimension

1770 mm

Known scale (the N in 1:N)

1

Target scale (the N in 1:N)

24

Printed scale-bar length

100 mm

Primary result: Target dimension: 73.7500 mm.

• Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
• Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
• When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.

This is a linear (single-axis) scale conversion, applied the same way to every dimension of a model - it does not adjust for parts that are deliberately not scaled linearly (some manufacturers slightly oversize fine details like figures' heads or vehicle mirrors so they stay visible at small scales).

For 3D-printing slicers specifically, always resize using a fixed scale factor uniformly on all axes unless you specifically want to distort the model - most slicers apply the percentage you enter to X, Y and Z together by default, but confirm your software's uniform-scaling setting before printing.