Example 1
- Radius: 10
1256.64
A ball of r = 10. Skin 1256.64, four circles of 314.16.
Sphere surface area calculator
Give the radius of the ball. You get the skin, four circle areas at the same r, not the water inside. At r = 10 a circle is 314.16 and the full surface is 1256.64; at r = 5 the skin drops fourfold to 314.16.
A = 4πr². Volume is on the sphere volume calculator. A disk is on the area of a circle calculator.
Result
Radius r (cm). Surface area shows up here.
How it works
Sphere surface area is four circle areas at the same radius. A = 4πr² leaves r squared, not cubed. The calculator uses π, not 22/7, and shows two decimals. The result is in cm² or in². That is paint, skin, wrapping, not liters inside.
The ball on the page has r = 10. One circle 314.16, skin 1256.64. At r = 5 the skin drops to 314.16, fourfold, and by a coincidence of formulas the same number as circle area at r = 10. The unit sphere r = 1 is 12.57. Further: r = 2 gives 50.27, r = 3 gives 113.10, r = 4 gives 201.06, r = 6 gives 452.39, r = 8 gives 804.25. At r = 3 the digits 113.10 also show up in sphere volume, two formulas, one numeric coincidence.
Type the radius, the same r as on the volume page, and click Calculate. If you know diameter, divide by two. Diameter 10 means r = 5 and 314.16; typing 10 as r gives 1256.64, four times too much because r is squared. A comma and a period are the same.
Volume at r = 10 is 4188.79, the 4/3 πr³ page. A cylinder has a different net: side 2πrh plus two lids. A cross-section great circle is πr², one quarter of this skin. Full 4πr² stays here.
Switching to inches relabels the result as in² and does not convert a typed 10. One r, one unit. Coat thickness and the number of layers sit outside the formula; here you only get the area to cover.
Halving the radius quarters the skin and eighths the volume. If you mix those two cards up, check the power: square is this page, cube is next door.
How to use
- Type the radius in cm or inches, the same r as on the volume page.
- Click Calculate. At r = 10 you get 1256.64, four circles of 314.16, with a cm² or in² label.
- If you know diameter, divide by two. Typing diameter as r overstates the skin by four.
- Volume is on the neighbouring page, formula 4/3 πr³. At r = 10 the interior is 4188.79.
- Open a cylinder with height and lids on its own cards. A sphere in this formula has no h.
Formula
A = 4 × π × r²
Four circle areas at the same r. Volume uses a cube of r and is next door.
A = 4πr² at r = 10
The skin, four circle areas. At r = 10 a circle is 314.16 and the full surface is 1256.64. At r = 5 the skin drops to 314.16.
- A
- Surface area 4πr². r = 10 is 1256.64. r = 1 is 12.57. r = 2 is 50.27. Not volume 4188.79.
- r
- Ball radius. 10 gives 1256.64. Half r = 5 gives 314.16, four times less.
- π
- Inside 4πr². Four circles of 314.16 at r = 10 stack to 1256.64.
Examples
Example 2
- Radius: 1
12.57
Unit sphere r = 1, 12.57.
Example 3
- Radius: 5
314.16
r = 5, 314.16. Same number as circle area at r = 10, different shape.
Example 4
- Radius: 2
50.27
r = 2, 50.27.
Example 5
- Radius: 3
113.10
r = 3, 113.10. Same digits as sphere volume at r = 3, two formulas.
Example 6
- Radius: 4
201.06
r = 4, 201.06.
Example 7
- Radius: 6
452.39
r = 6, 452.39.
Example 8
- Radius: 8
804.25
r = 8, 804.25.
Frequently asked questions
How much skin at r = 10?
1256.64, four circles of 314.16. Volume at that r is 4188.79, another page.
Is this sphere volume?
This is 4πr², the skin. Volume 4/3 πr³ at r = 10 is 4188.79; here it is 1256.64.
Why does r = 5 give 314.16, the same as a circle at r = 10?
Because 4π×25 = 100π, and circle area at r = 10 is also 100π. Different shape, same number.
Is diameter 10 the same as r = 10?
Diameter 10 means r = 5 and 314.16. Typing 10 as r gives 1256.64.
Is this cylinder lateral area?
A cylinder uses 2πrh plus optional lids. A sphere has no height in this formula.
How does area drop if r is halved?
Fourfold, because r is squared. Volume would drop eightfold. At r = 10 and r = 5 you see 1256.64 versus 314.16.
Is π 22/7?
The calculator uses π. At r = 1 the display is 12.57 to two places.
How do I use this number to paint a sphere?
It is the area to cover. Coat thickness is outside the formula. This page is only the skin.
Is a great circle on this page?
A great circle is πr², one quarter of this skin. At r = 10 that is 314.16. Full 4πr² stays here.
Why does r = 3 give 113.10, the same as sphere volume at r = 3?
A coincidence of two formulas. 4π×9 and 4/3 π×27 land on the same number. Different units, different cards.
Knowledge sources
The calculator computes the same formula as the definition below.
Page updated in 2026.