RadiusMapperFree Map Radius Calculator
Radius Calculator
Radius Calculator Map — Area, Circumference, and Drive-Time From Any Address
A free radius calculator map. Use the formula table below for straight-line math (area and circumference). Use the map tool above for a real drive-time radius from any address. The drive-time number is the one that actually matters for service zones, commutes, and catchments.
Drive-time radius from any address
Interactive drive-time radius map
What is a radius math (straight-line)?
The area enclosed by a radius circle is A = pi x r^2. The circumference is C = 2 x pi x r. These formulas describe geometric proximity and ignore the road network.
- A 10-mile radius covers 314.2 square miles - larger than San Francisco (46.9 sq mi) and Washington D.C. (68.3 sq mi) combined
- A 25-mile radius covers 1,963.5 square miles - roughly the size of Delaware (1,954 sq mi)
- A 50-mile radius covers 7,854 square miles - slightly larger than New Jersey (7,354 sq mi)
- A 100-mile radius covers 31,416 square miles - roughly the size of South Carolina (30,061 sq mi)
Straight-line radius answers 'how far' geometrically. Drive-time radius (the map above) answers 'how far can I actually go in X minutes' - usually the more useful number.
Radius quick reference table (miles)
| Radius (miles) | Area (sq miles) | Circumference (miles) |
|---|---|---|
| 1 miles | 3.1 | 6.3 |
| 5 miles | 78.5 | 31.4 |
| 10 miles | 314.2 | 62.8 |
| 15 miles | 706.9 | 94.2 |
| 25 miles | 1,963.5 | 157.1 |
| 50 miles | 7,853.9 | 314.2 |
| 100 miles | 31,415.9 | 628.3 |
| 150 miles | 70,685.8 | 942.5 |
Radius formulas
Area
A = pi x r²
For a 10-mile radius: 3.14159 x 100 = 314.2 square miles
Circumference
C = 2 x pi x r
For a 10-mile radius: 2 x 3.14159 x 10 = 62.8 miles around the boundary
Radius from area
r = sqrt(A / pi)
To cover 500 sq miles: sqrt(500 / 3.14159) = 12.6 miles
Related tools
Frequently asked questions
How do you calculate the area of a radius?
Area = pi x radius squared. For a 10-mile radius: 3.14159 x 100 = 314.2 square miles. For a 25-mile radius: 1,963.5 square miles.
How many square miles is a 10-mile radius?
314.2 square miles. That is larger than San Francisco (46.9 sq mi) and roughly the size of the core Chicago metro.
How many square miles is a 25-mile radius?
1,963.5 square miles - about the size of Delaware (1,954 sq mi) or the Dallas-Fort Worth metro area.
How do I convert radius to diameter?
Diameter = radius x 2. A 10-mile radius has a 20-mile diameter and a 62.8-mile circumference.
What radius covers 1 square mile?
Radius = sqrt(1 / pi) = 0.564 miles, or about 2,975 feet.
What is a drive-time radius?
The boundary of all locations reachable from a starting point within a given travel time, traced along the road network. The map tool above draws drive-time radii from any address - more useful than a straight-line circle for service area or commute analysis.
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