Scale Calculator

How to use the Scale Calculator

1. 1Enter the scale number, whether you know the drawing or the real size, the length and its unit.
2. 2Pick the units or options from the menus if the map or model scale tool offers them.
3. 3Read the map or model scale in the large result box.
4. 4Look at the extra rows for related figures.
5. 5Press Copy result to keep the answer.

When you need the map or model scale

Architects and builders read plans at scales such as 1:20, 1:50 and 1:100. Hikers use map scales like 1:25,000 to turn centimetres on the map into kilometres on the ground. Model makers use 1:24, 1:48 or 1:72 for cars, planes and railways.

The scale applies to lengths only. Areas change with the square of the scale: at 1:50, a drawing area of 1 cm² stands for 2,500 cm² in reality. Volumes change with the cube.

How the map or model scale is worked out

Real size = drawing size × scale number. Drawing size = real size ÷ scale number. On a plan at 1:50, a wall that measures 4 cm is 2 m long in real life. A 30 cm toy at 1:24 stands for an object 7.2 m long. A 2 inch measurement on a 1:1000 map is 50.8 m on the ground.

Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.

• Either direction
• Eight units
• Works for maps and models

Mistakes to avoid with map or model scale

Type only the number after the colon: for 1:50 type 50. Do not mix up the two directions: converting from the drawing gives a larger real size, from real size gives a smaller drawing. Printed plans can be shrunk by a printer, so check the scale bar.

On phone and computer

On a phone, type into the boxes one after another and read the map or model scale underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the map or model scale move. The scale calculator works the same on both. Scale sums often involve unit changes, so keep those tools close. Use the Unit Converter to change units, the Aspect Ratio Calculator for pictures, and the Ratio Calculator for any proportion.

Features

• Areas scale by the square
• Check the scale bar after printing
• Only the number after the colon
• Clear messages when the map or model scale inputs make no sense
• Copy the result with one tap
• Private: nothing is uploaded

Frequently asked questions