Water Measurement Unit Converter
Convert between U.S. Customary (USCS) and International System (SI) units commonly used in irrigation and water management: volume, flow, length, and area.
Converter
Water Weight Equivalence
Applies to water only, at standard conditions (1 gal water ≈ 8.33 lb; 1 L water ≈ 1 kg). Useful for converting an applied water volume to a mass, e.g. for fertigation calculations.
Reference: Table 3.1 — Conversion Factors Used in Water Measurement
| U.S. Customary System (USCS) | Conversion between USCS and SI | International System (SI) |
|---|---|---|
| Volume Units | ||
| 1 gal = 8.33 lb | 1 ft³ = 0.02832 m³ | 1 L = 1,000 cm³ |
| 1 ft³ = 7.48 gal | 1 L = 0.264 gal | 1 cm³ = 0.001 L |
| 1 ac-in = 3,630 ft³ | 1 gal = 3.79 L | 1 m³ = 1,000 L |
| 1 ac-in = 27,154 gal | 1 m³ = 264.2 gal | 1 L = 0.001 m³ |
| 1 ac-ft = 43,560 ft³ | 1 ac-in = 1.028 ha-cm | 1 ha-cm = 100 m³ |
| 1 ac-ft = 325,851 gal | ||
| Flow Units | ||
| 1 cfs = 449 gpm (450 for practical purposes) | 1 cfs = 0.02832 cms | 1 L/s = 1,000 mL/s |
| 1 cfs = 1 ac-in/hr | 1 cms = 35.31 cfs | 1 cms = 60,000 L/min* |
| 452 gpm (450 for practical purposes) = 1 ac-in/hr | 1 gpm = 0.06309 L/s | |
| 1 gpm = 0.00223 cfs | 1 L/s = 15.85 gpm | |
| 1 gpm = 0.00221 ac-in/hr | 1 gal/h = 1.05 mL/s* | |
| Length Units | ||
| 1 mile = 5280 ft | 1 ft = 0.3048 meters | 1 cm = 0.01 meter |
| 1 rod = 16.5 ft | 1 meter = 3.281 ft | 1 meter = 100 cm |
| 1 km = 1,000 meter | ||
| Area Units | ||
| 1 ac = 43,560 ft² | 1 ac = 0.4047 ha | 1 ha = 10,000 m² |
| 1 ha = 2.471 ac | ||
cfs = cubic feet per second • cms = cubic meters per second • gpm = gallons per minute • L/s = liters per second
* The printed textbook lists these two values as "1 cms = 16.7 L/min" and "1 gal/h = 63.1 mL/s," which don't hold up dimensionally (1 cms is 1 m³/s = 60,000 L/min, and 1 gal/h ≈ 1.05 mL/s — the printed 63.1 mL/s is actually 1 gal/min). They've been corrected here so the reference table is dimensionally accurate for the units labeled.
The calculator above uses precise conversion factors internally (rather than the rounded values shown in this reference table) so that chained conversions stay accurate.