What Is 1/25 Scale? | Model Sizes Made Simple

1/25 scale means one unit on a model equals 25 units on the real object, making the model 4% of full size.

This scale is most familiar to hobbyists building model car kits and to architects laying out detailed drawings. The math works the same in both worlds — the only difference is where you apply it.

The Simple Conversion Math

Converting sizes with 1/25 scale takes one operation in each direction. Divide a real-world measurement by 25 to get the model size; multiply a model measurement by 25 to return to full size.

• Real to model: 25-foot truck ÷ 25 = 1-foot model
• Model to real: 4 cm model × 25 = 100 cm real object
• Metric rule: 1 meter in reality = 4 centimeters on the model

The same math works for every dimension — length, width, and height. Measure one side, divide by 25, and you have the matching model measurement.

Where 1:25 Scale Actually Shows Up

The 1/25 ratio appears in three main places: model car kits, architectural drawings, and collectible resin models. Model car builders know it best — AMT and Round 2 kits use 1/25 as a standard hobby scale, and it is the most common size for American car and truck kits.

Architects and engineers use 1:25 as a technical drawing scale, where one unit on the plan equals 25 units in reality. This larger magnification suits detailed zoomed-in views like stairwells and room layouts. That said, 1:25 is less common than broader scales like 1:50 or 1:100, which fit full building layouts on standard sheets.

For anyone shopping for diecast or resin pieces, the scale label on the box tells you the model will be roughly 4% of the real vehicle’s length.

How To Read A 1:25 Scale Ruler

Scale rulers make the conversion visual instead of mathematical. To use one, align the zero mark on the 1:25 side of the ruler with one end of your measurement, then read the corresponding mark on that same 1:25 edge. The key is using the correct side — a ruler with multiple scale ratios prints each one on a separate edge, so a 1:50 reading will be wrong on a 1:25 drawing.

When no ruler is handy, the divide-by-25 formula gives the same result. Measure the real object in inches or centimeters, divide by 25, and you get the model dimension in the same unit.

Common Mistakes With 1/25 Scale

Two errors trip up new modelers and drafters. First, 1:25 and 1:24 are close cousins but not interchangeable — 1:24 is roughly 4% larger. That difference is invisible on small parts but obvious on full car bodies, so a 1:24 part will not fit a 1:25 kit.

If you’re thinking about picking up a kit, our roundup of the best 1 25 scale model cars covers the top builds worth your bench space.

The Bottom Line On 1/25 Scale

1/25 scale is a 1:25 reduction ratio that makes any model exactly 4% of full size. Divide real dimensions by 25 to find the model size, multiply model dimensions by 25 to find the real size, and keep 1:24 parts away from 1:25 models — they are close but not compatible. For model car kits and detailed architectural drawings, that one rule is all you need.