Acre Foot Of Water Calculator

Calculate the missing length, width, depth, or volume in acre-feet from three values using ft, m, in, yd, cubic feet, cubic meters, or liters.

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Acre Foot Of Water Formula

The acre-foot of water calculation starts with rectangular volume. Convert length, width, and depth to feet, multiply them to get cubic feet, then divide by 43,560 to convert cubic feet to acre-feet.

V₍af) = (L₍ft) \times W₍ft) \times D₍ft)) / (43560)

V_af = volume in acre-feet
L_ft = length in feet
W_ft = width in feet
D_ft = depth in feet
43,560 = cubic feet in 1 acre-foot when water covers 1 acre to a depth of 1 foot

If you know the volume and need one missing dimension, rearrange the formula:

L₍ft) = (V₍af) \times 43560) / (W₍ft) \times D₍ft))

W₍ft) = (V₍af) \times 43560) / (L₍ft) \times D₍ft))

D₍ft) = (V₍af) \times 43560) / (L₍ft) \times W₍ft))

Length function: uses acre-feet, width, and depth to solve for the missing length.
Width function: uses acre-feet, length, and depth to solve for the missing width.
Depth function: uses acre-feet, length, and width to solve for the missing depth.
Volume function: uses length, width, and depth to calculate water volume, then converts the result to the selected volume unit.

Acre-Foot Water Volume Conversions

These common conversions help you interpret acre-foot results in other volume units.

Volume	Equivalent
1 acre-foot	43,560 cubic feet
1 acre-foot	About 325,851 gallons
1 acre-foot	About 1,233.48 cubic meters
1 acre-foot	About 1,233,480 liters

Typical Depths Over One Acre

For a 1-acre surface area, the acre-foot value is the same as the water depth in feet.

Water Depth Over 1 Acre	Volume
1 inch	0.0833 acre-feet
6 inches	0.5 acre-feet
1 foot	1 acre-foot
2 feet	2 acre-feet

Example Problems

Example 1: Find acre-feet from length, width, and depth

You have a pond that is 300 ft long, 150 ft wide, and has an average depth of 4 ft.

V₍af) = (300 \times 150 \times 4) / (43560)

V₍af) = (180000) / (43560) = 4.1322

The pond contains about 4.13 acre-feet of water.

Example 2: Find depth from acre-feet

You know a rectangular water area is 660 ft long, 330 ft wide, and contains 5 acre-feet of water.

D₍ft) = (5 \times 43560) / (660 \times 330)

D₍ft) = (217800) / (217800) = 1

The average depth is 1 ft.

FAQ

What is an acre-foot of water?

An acre-foot is the amount of water needed to cover 1 acre of area with 1 foot of water. Since 1 acre equals 43,560 square feet, 1 acre-foot equals 43,560 cubic feet of water.

Why does depth matter when calculating acre-feet?

Acre-feet measure volume, not just surface area. A larger area with shallow water can have the same acre-feet as a smaller area with deeper water. You need length, width, and average depth to estimate the total amount of water.

Should I use average depth or maximum depth?

Use average depth. Maximum depth usually overstates the total water volume because most ponds, reservoirs, and basins are not the same depth everywhere. If the bottom is uneven, estimate the average depth from several depth measurements.

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