Scale Converter
Real and scaled lengths for drawings, maps and models, in mixed units.
Try before you buy.
- Free preview: the rules, dates and checks that apply to your figures, with every computed amount hidden.
- Locked until you unlock it: download and copy.
- Unlock: Pro pass, ₹179 for 30 days or ₹79 for 1 week, a one-time payment that never renews. Unlock: Pro pass, $5.99 for 30 days or $2.99 for 1 week, a one-time payment that never renews.
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Locked in the free preview. Opens the ways to unlock this result.
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Locked in the free preview. Query results unlock with a pass.
About the Scale Converter
Convert a length between real size and its size on a drawing, map or model. Give the scale as a ratio such as 1:50, 1:250000 or HO’s 1:87.1, or as an equality in any units, such as 1/4 in = 1 ft (architectural, 1:48), 1 in = 20 ft (engineering, 1:240) or 1 cm = 2.5 km (a map at 1:250,000). Lengths can be decimals, fractions such as 3/8 or 1 1/2, or feet and inches such as 4' 6". To find a drawing’s scale, measure one length on the paper and its real length, and the converter works out the ratio.
The free preview shows the result rows with the values hidden; a Pro pass shows every value, with copy and text or JSON downloads.
How to use it
- Choose Use a scale, or Find the scale from two measurements.
- Enter the scale (for example 1:50 or 1/4 in = 1 ft), or a length measured on the paper or model and the same length in real life, each with its unit.
- Choose the direction, enter the length to convert with its unit, and choose the unit of the result.
- Select Convert; with a Pro pass, copy the working or download it as text or JSON.
Formulas and common scales
A scale of 1:n means that one unit on the paper or model stands for n of the same unit in real life, so a real length is the scaled length times n, and a scaled length is the real length divided by n. An equality such as 1/4 in = 1 ft becomes a ratio once both sides are in the same unit: 1 ft ÷ 0.25 in = 48, so 1:48. Common model railway scales include HO at 1:87.1, N at 1:160 and O at 1:48 (NMRA standards); 1:24, 1:43 and 1:72 are common for model cars and aircraft.
Limitations
- The arithmetic is exact, but a printed or scanned drawing may not be at its stated scale: check it against a dimension written on the drawing.
- This converts lengths, not areas or volumes: an area scales with the square of the ratio.
Privacy
On this device: nothing is sent
Every value is calculated on your device; nothing is uploaded or stored.
Frequently asked questions
What do I get without a pass?
Without a pass, Scale Converter shows the rules, dates and checks that apply to your figures, with every computed amount hidden. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
How do I read 1/4 inch = 1 foot?
A quarter of an inch on the drawing stands for one foot in real life. A foot is 48 quarter-inches, so the scale is 1:48.
How do I find the scale of a drawing?
Choose Find the scale, enter a length you measured on the drawing (for example 25 mm) and the real length it shows (for example 5 m). The converter gives 1:200 and converts other lengths with it.