Understanding Gallon per Minute and Cubic Foot per Second
A gallon per minute (gal/min) measures how many US liquid gallons flow each minute. It is common in plumbing, irrigation, and fuel‑pump specifications.
A cubic foot per second (ft³/s) measures how many cubic feet of fluid pass a point each second. Engineers often use it in HVAC, fire‑suppression design, and industrial process calculations.
Why Convert Between These Units?
- Designing a sprinkler system may require the flow rate in ft³/s, while the pump’s rating is in gal/min.
- Energy‑use models for water utilities often standardize on ft³/s for consistency.
- International projects may mix US‑customary and metric‑friendly units, making a reliable conversion essential.
Exact Conversion Factor
The relationship is fixed by the volume definitions:
- 1 US gallon = 0.133681 cubic feet.
- 1 minute = 60 seconds.
Therefore, 1 gal/min = 0.002228 ft³/s (rounded to six decimal places for clarity).
Conversion Formula
To change a flow rate from gallons per minute to cubic feet per second, multiply by the factor 0.002228:
ft³/s = (gal/min) × 0.002228
If you need the reverse, divide by the same factor.
Worked Example: From Gal/min to Ft³/s
Suppose a garden pump delivers 75 gal/min. How many cubic feet per second is that?
- Write the known value: 75 gal/min.
- Apply the formula: 75 × 0.002228 = 0.1671 ft³/s.
- Round to a practical precision: 0.167 ft³/s.
The pump moves roughly 0.167 cubic feet of water each second—useful when sizing downstream piping.
Gallon Per Minute to Cubic Foot Per Second Conversion Table
Each row applies the same rule: multiply gallons per minute by 0.002228 ft³/s per gal/min.
| Gallon per Minute (gal/min) | Cubic Foot per Second (ft³/s) |
|---|---|
| 1 gal/min | 0.002228 ft³/s |
| 2 gal/min | 0.004456 ft³/s |
| 5 gal/min | 0.01114 ft³/s |
| 10 gal/min | 0.02228 ft³/s |
| 20 gal/min | 0.04456 ft³/s |
| 50 gal/min | 0.1114 ft³/s |
| 100 gal/min | 0.2228 ft³/s |
| 500 gal/min | 1.114 ft³/s |
Practical Tips for Using This Conversion
- Check your gallon type. The factor above uses the US liquid gallon. UK gallons differ (1 UK gal = 0.16054 ft³).
- Round consistently. For engineering reports, keep four significant figures; for quick field checks, two may suffice.
- Combine with pressure data. Flow rate alone doesn’t define system performance; pair it with pressure loss calculations for pipe sizing.
Conclusion
Converting gallon per minute to cubic foot per second is a simple multiplication: 1 gal/min = 0.002228 ft³/s. With the formula, a worked example, and a ready‑to‑use table, you can translate any flow‑rate figure instantly. Need more conversions or a custom calculator? Explore our full suite of unit‑conversion tools and keep your projects flowing smoothly.