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Scale Converter
Shrink real-world dimensions to a model, plan or drawing scale, or measure a model or drawing and get the real size. Type feet and inches like 12' 6" or metric units, and pick from model railway, diecast, architectural and engineering scales.
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Convert
Enter your values to see the result.
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How to use the Scale Converter
- Choose a direction: real size to scale, or scale to real size.
- Pick the scale, for example 1:87 (HO) or 1/4" = 1', or enter a custom ratio.
- Choose the units you will type and enter the length, plus width and height if you like.
- Press Convert to get the scaled or real dimensions in inches (to 1/16) and metric.
- Compare scales in the table to see the same object at other common scales.
How scale conversion works
A scale is a ratio 1 : N: one unit on the model or drawing stands for N of the same units in real life. Because it is a pure ratio, it works in any unit system.
- Real to scale:
scale size = real size ÷ N - Scale to real:
real size = scale size × N
Architectural scales are written as a drawing length per real foot. To get N, divide 12 inches by the drawing length: 1/4" = 1' gives 12 ÷ 0.25 = 48, so it is 1:48. Engineering scales give real feet per drawing inch: 1" = 30' is 30 × 12 = 1:360.
Example: a room 14' 3" long drawn at 1/4" = 1'. 14' 3" is 171 inches, and 171 ÷ 48 = 3.5625 in, which is 3 9/16 inches on the plan.
Common scales at a glance
| Scale | Ratio | 1 real foot on the model | Typical use |
|---|---|---|---|
| 1" = 1' | 1:12 | 1 in (25.4 mm) | Dollhouses, furniture details |
| 1/2" = 1' | 1:24 | 1/2 in (12.7 mm) | Model cars, half-scale dollhouses, details |
| 1/4" = 1' | 1:48 | 1/4 in (6.35 mm) | House floor plans, O gauge trains |
| 3/16" = 1' | 1:64 | 3/16 in (4.8 mm) | S gauge trains, toy cars |
| 1/8" = 1' | 1:96 | 1/8 in (3.2 mm) | Larger building plans |
| HO | 1:87 | 0.138 in (3.5 mm) | The most popular model railway scale |
| N | 1:160 | 0.075 in (1.9 mm) | Compact model railways |
| 1" = 20' | 1:240 | 0.05 in (1.27 mm) | Site plans, civil drawings |
Tips
- Areas and volumes scale differently: at 1:48 a floor area shrinks by 48² = 2,304 times, and a volume by 48³. Convert each length, then multiply.
- Check printed drawings: a plan printed "to fit" the paper is no longer at its stated scale. Measure a known dimension first.
- Model railway gauge vs scale: gauge is the track width; scale is the size ratio. HO is 1:87 scale on 16.5 mm gauge track.
- For a quick ratio like 3:4 or to find a missing value, the Ratio Calculator also helps.
Frequently asked questions
How do I convert a real measurement to scale?
Divide the real size by the scale number. At 1:87 (HO), a 50-foot boxcar is 600 inches ÷ 87 = 6.9 inches long. To go back, multiply the model size by the scale number.
What ratio is 1/4 inch = 1 foot?
1/4 inch = 1 foot is 1:48, because one foot is 12 inches and 12 ÷ 0.25 = 48. Likewise 1/8" = 1' is 1:96, 1/2" = 1' is 1:24 and 1" = 1' is 1:12.
What does HO scale 1:87 mean?
Every dimension on an HO model is 1/87 of the real thing, so 1 inch on the model represents about 7 feet 3 inches in real life, and one real foot is about 0.14 inch (3.5 mm).
How do I read an engineering scale like 1 inch = 20 feet?
One inch on the drawing equals 20 feet (240 inches) on the ground, a ratio of 1:240. Measure the drawing in inches and multiply by 20 to get feet.
Which model scale is bigger, 1:24 or 1:48?
1:24 is twice as big as 1:48. The smaller the second number, the larger the model: a 1:24 car is about 7 inches long, the same car at 1:48 is about 3.5 inches.
Can I enter feet and inches?
Yes. With feet & inches selected you can type 12' 6", 12 ft 6 in, 12-6" or just 12 6. A single number is read as feet, and inch fractions like 6 1/2" work too.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
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