A map scale tells you how distances on the map relate to distances on the ground. Read it correctly and you can measure a route, size a property, or tell whether a map is detailed enough for the job.
Three ways to show scale
- Representative fraction (RF), such as 1:24,000. One unit on the map equals 24,000 of the same unit on the ground: 1 inch is 24,000 inches, 1 cm is 24,000 cm. It works in any unit.
- Verbal scale, such as "1 inch = 2,000 feet". The same scale in words, easy to use but tied to particular units.
- Graphic or bar scale, a ruler printed on the map. It's the only one that stays correct when a map is enlarged, shrunk or shown on a screen.
To get from RF to a verbal scale, divide by the number of map units in a ground unit: 24,000 inches ÷ 12 = 2,000 feet. In metric, 1:24,000 means 1 cm = 24,000 cm = 240 m.
| Scale | 1 inch equals | 1 cm equals | Typical use |
|---|---|---|---|
| 1:1,200 | 100 ft | 12 m | Site and engineering plans |
| 1:2,400 | 200 ft | 24 m | Parcel and tax maps |
| 1:24,000 | 2,000 ft (0.38 mi) | 240 m | USGS 7.5-minute topographic maps |
| 1:63,360 | 1 mile | 634 m | "Inch to the mile" maps |
| 1:100,000 | 1.58 mi | 1 km | County and regional maps |
| 1:250,000 | 3.95 mi | 2.5 km | Regional overview maps |
| 1:1,000,000 | 15.8 mi | 10 km | Country and world maps |
Large scale vs small scale
This confuses almost everyone. Large scale means a large fraction: 1:1,200 is bigger than 1:1,000,000 (1/1,200 vs 1/1,000,000). Large-scale maps show a small area in great detail. Small-scale maps show a large area with little detail. A quick test: the smaller the number after the colon, the larger the scale and the closer you are.
Measuring a distance on a map
- Measure the distance on the map with a ruler. Say it's 3.2 inches.
- Multiply by the scale's ground distance per unit: 3.2 × 2,000 ft = 6,400 ft at 1:24,000.
- Convert if needed: 6,400 ÷ 5,280 ≈ 1.21 miles.
That's a straight-line distance. Roads and trails wind, so the travel distance is longer. For straight-line distances between two coordinates, a distance calculator skips the ruler entirely.
Scale on screens and web maps
Once a map is on a screen, its RF depends on the screen size and zoom, so a printed "1:24,000" no longer holds. Web maps in the Web Mercator projection also change scale with latitude: features far from the equator are drawn larger than they are. Rely on the bar scale, and remember that one bar may not be accurate across a whole country.
Frequently asked questions
Is 1:50,000 more detailed than 1:25,000?
No. 1:25,000 is the larger scale and shows more detail; 1:50,000 covers four times the area on the same sheet.
Why do maps say 'not to scale'?
The drawing is diagrammatic, like a transit map, so distances can't be measured from it.
What scale should my project map be?
It depends on the smallest feature people need to see and the paper size. For a single site, 1:1,200 to 1:2,400 is common; for a town, 1:24,000 or smaller.
Need maps at the right scale?
We design print and web maps people can actually read.
From site plans to regional atlases, at the scale the decision needs.