Map Scale Calculator

Pre-Algebra · Axiom Academy

A map scale like "1 inch = 50 miles" is a ratio. Set up a proportion and you can convert any map distance into a real one — and back. On the map below, Riverside and Springfield are 3.5 inches apart. The legend reads 1 inch = 50 miles . That little equation is a ratio : every single inch of paper stands for 50 real miles. Watch each measured inch unfold into its 50-mile chunk of real road. Each map inch buys 50 real miles 2. Turn the Ratio Into a Proportion Because the rate never changes, the ratio of map inches to real miles is the same for any distance. Line the map ruler up against the real-distance ruler: at every point, the small ratio 1 : 50 equals the big ratio of your two distances. That equal-ratios statement is a proportion . Same rate on both sides — that's a proportion Hold a ruler to the map and read the inches between the two points. Here it's 3.5 in. 1 inch : 50 miles. This is the bridge that links paper to ground. The actual miles you want. Solve the proportion for it. Multiply the map inches by 50 (or cross-multiply) to find the real miles. 1 inch is to 50 miles as 3.5 inches is to r miles. The two rulers stay locked together no matter where the slider sits — that's what makes the conversion trustworthy. 3. Solve It: 3.5 Inches Becomes 175 Miles Now finish the original problem. We measured 3.5 inches and the scale is 1 inch = 50 miles . To go from paper to ground, multiply the map distance by the scale factor. Watch the × 50 sweep in and land the answer.

This is the written version of the interactive lesson above. See the full Pre-Algebra course.