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Interactive tool

Map scale & distance

Turn a ruler measurement on a fixed-scale map into an estimated ground distance. Works with metric and imperial input units.

Ground distance

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Enter values to calculate a ground distance.

Formula

ground distance = map distance × scale denominator

The tool converts the measurement to metres before calculating, then converts the result to your selected unit.

Worked example

At 1:50,000, one centimetre on the map represents 50,000 centimetres, or 500 metres, on the ground. A 4 cm map distance therefore represents 2 km.

Accuracy and limitations

A printed or exported map must not have been resized after its scale was set.
A straight ruler measurement underestimates a winding road, river, or trail.
Small-scale maps generalize curves and boundaries.
Web maps change scale as you zoom; use the visible scale bar instead of assuming a fixed ratio.
Distance measured in a projected map can differ from geodesic distance, especially over large areas.

Try it

Calculate the ground distance for 3.2 inches on a 1:24,000 map. Report the answer in miles.

Show answer

3.2 × 24,000 = 76,800 inches, which is about 1.212 miles. The precision of the source measurement does not justify many extra decimal places.