Tank Fill Time Calculator
Estimate source water volume, effective fill rate, fill duration and cost between current and target tank levels.
Default project preview
1.14 hours
Stored volume added
650 gal
Source volume needed
684.2 gal
Effective fill rate
9.5 gal/min
Starting volume
250 gal
Calculator
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Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Tank capacity
Enter this project assumption in gal. The current imperial default is 1000 gal.
Current level
Enter this project assumption in %. The current imperial default is 25 %. Minimum: 0. Maximum: 100.
Target level
Enter this project assumption in %. The current imperial default is 90 %. Minimum: 0. Maximum: 100.
Source flow
Enter this project assumption in gal/min. The current imperial default is 10 gal/min.
Fill loss
Enter this project assumption in %. The current imperial default is 5 %. Minimum: 0. Maximum: 50.
Water price
Enter this project assumption in per 1,000 gal. The current imperial default is 5 per 1,000 gal. Minimum: 0.
How to read the outputs
Stored volume added
tank-level increase. Default preview: 650 gal.
Source volume needed
loss included. Default preview: 684.2 gal.
Effective fill rate
after entered loss. Default preview: 9.5 gal/min.
Starting volume
current level. Default preview: 250 gal.
Ending volume
target level. Default preview: 900 gal.
Water cost
source volume and entered rate. Default preview: $3.42.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Stored volume = capacity × level increase. Source volume = stored volume ÷ fill efficiency. Fill time = source volume ÷ source flow.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: August 19, 2026
Estimate how much source water and time are required to raise a tank from one percentage level to another while accounting for an entered fill-loss percentage.
Calculation steps
- 1Calculate the target level increase as a fraction of total usable tank capacity.
- 2Convert stored volume to source volume by dividing by fill efficiency.
- 3Divide source volume by measured source flow for fill duration.
- 4Use source volume, not stored volume, when estimating purchased water cost.
Worked numerical example
A 1,000 gal tank raised from 25% to 90% stores 650 gal. With 5% fill loss, the source must supply about 684 gal. At 10 gpm, ideal fill time is about 68.4 minutes.
Purchasing and rounding
Verify usable rather than nominal tank capacity and measure actual sustained fill flow. Float-valve restriction, pressure changes and pump cycling can lengthen real fill time.
Interpret the result
The stored-volume result is what remains in the tank; source volume is higher when losses are entered. Fill time assumes the source flow stays constant.
Page-specific assumptions
- Tank percentage corresponds linearly to usable volume.
- Source flow is approximately constant.
- Entered loss represents water not retained in the tank.
Common mistakes
- Using total tank capacity instead of the change in level.
- Multiplying by loss instead of dividing by fill efficiency.
- Assuming pump nameplate flow equals delivered flow at the tank.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Tank Fill Time Calculator questions
Why can source volume exceed stored volume?+
Entered losses represent water that does not remain in the tank because of flushing, leakage or process loss.
Can flow rate change during filling?+
Yes. Pressure and pump operation can make the actual rate vary over time.
Does this prevent tank overflow?+
No. Use appropriate level controls, overflow paths and supervision.