Tank fill time Calculator: measuring notes and method
Enter only the remaining volume
If a 1,000 L tank already contains 300 L, enter 700 L to fill. At a constant 20 L/min, the remaining fill takes 35 minutes.
Use net flow when applicable
If a known constant outflow continues, subtract it from inflow before calculating. Falling inlet pressure, a float valve or varying pump output can make the actual time longer than a constant-flow estimate.
Formula
Fill time = volume to add ÷ constant flow rate.
Worked examples in metric and imperial units
Illustrative values match Reset example and stay fixed when you edit the calculator. Both columns describe the same calculation; converted inputs are rounded.
Metric worked example
- Volume to add
- 1,000 L
- Constant flow rate
- 20 L/min
Fill time: 0.8333 hours
Imperial worked example
- Volume to add
- 264.1721 US gal
- Constant flow rate
- 5.2834 US gal/min
Fill time: 0.8333 hours
Follow the calculation
- Time = 1,000 ÷ 20 = 50 minutes.
- Divide minutes by 60 to obtain 0.833333 hours.
Unit conversions
Liquid conversions use US gallons (3.785411784 L), not UK imperial gallons (4.54609 L).
Reviewed 19 October 2026. How calculations are checked · Report a correction