Tank Fill Time Calculator
Estimate tank fill time from capacity, current level, inflow and simultaneous outflow
Estimated fill time
How we calculated it
About the Tank Fill Time Calculator
Tank fill time estimates how long a tank takes to fill from a known flow rate. It is useful for water storage, irrigation and process planning when tank volume and inflow are known.
Actual filling can slow if pump flow changes with pressure or if the tank is already partially full.
How to Use the Tank Fill Time Calculator
- Enter tank capacity or remaining volume to fill.
- Enter the inflow rate.
- Choose compatible volume and time units.
- Calculate fill time and account separately for changing pump flow or interruptions.
How the Calculation Works
Volume still required = total tank capacity − current volume when the tank is partly full. For a constant positive inflow with no simultaneous outflow, fill time = remaining volume ÷ inflow rate.
If water is entering and leaving at the same time, net fill rate = inflow − outflow and fill time = remaining volume ÷ net fill rate. A zero or negative net rate means the tank will not reach a higher level under those conditions.
Worked example
Tank Fill Time Calculator Worked Example
2,000 L tank filled at 40 L/min
Fill time = 2,000÷40 = 50 minutes from empty at a constant flow rate.
Result guide
Understanding Your Tank Fill Time Calculator Result
The result assumes constant flow. A pump whose output falls as head pressure rises can take longer in practice.
Before you rely on the answer
Assumptions and Limitations
- Flow rate remains approximately constant.
- Tank volume and flow use compatible units.
- Leakage, interruptions and overflow-control delays are excluded.
Practical tip
Using This Result in Practice
Measure actual flow at the tank when possible rather than relying only on a pump’s maximum rating. Pipe restrictions and lift can reduce delivered flow. If both inflow and outflow occur at the same time, use net flow rather than inlet flow alone. Net fill rate equals inflow minus outflow, and the tank will not fill if the net rate is zero or negative.
Related calculations
Useful Calculations to Continue With
If tank capacity is not already known, calculate it first with the Tank Volume Calculator.
If the flow is reported in a different unit, use the Flow Rate Converter before calculating fill time.
Common questions
Tank Fill Time Calculator FAQ
How do I calculate tank fill time?
Divide the volume that still needs to be filled by the inflow rate.
Why might a real tank take longer to fill?
Pump flow can vary with pressure, pipe resistance and supply conditions.
Can I use total tank capacity if it is already partly full?
No. Subtract the current volume first and calculate only the remaining volume to fill.