Tank Fill and Drain Time

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Tank Fill and Drain Time

Tank Fill and Drain Time Calculation:

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V =
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Tank Volume

The usable amount of liquid in the tank, pool, reservoir, tote, or container. Use the helper below if you need to calculate this from dimensions or choose a common size.
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Vu =
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Volume Unit

Choose the unit used for the tank volume.
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Q =
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Flow Rate

How much liquid flows per unit of time. If you do not know the rate, use the estimates and measurement helper below.
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Qu =
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Flow Rate Unit

Choose the unit used for the fill or drain rate.
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A =
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Fill or Drain

Use fill for adding liquid and drain for removing liquid. If the level direction does not match the action, the calculator swaps the starting and target levels.
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S% =
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Starting Level

Starting level as a percent of usable volume, not measured liquid height. For empty-to-full filling, use 0.
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T% =
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Target Level

Target level as a percent of usable volume, not measured liquid height. For full draining, use 0 with a starting level of 100.
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t =
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Time

Estimated time for the selected tank volume, flow rate, and level change.
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D =
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Amount Moved

The volume actually filled or drained after the starting and target levels are applied.
Decimals

Choose the number of decimals to show in your answer. This is also known as significant figures. Select an appropriate amount of significant figures based on the precision of the input numbers.

Tank Fill and Drain Time Answer

Enter a tank or pool size, enter a fill or drain rate, and the calculator will estimate the time. If you do not know the tank size or rate yet, use the helpers below and send the result back into the calculator.

Answer

10 U.S. gallons at 2 gpm fills from 0% to 100% in about 5 min.

Moving 10 U.S. gallons at 2 U.S. gallons per minute.

300total seconds

5minutes

0.08hours

0days

10U.S. gallons moved

38liters moved

2U.S. gpm

10 U.S. gallons at 2 gpm fills from 0% to 100% in about 5 min.

Flow rates can vary with hose length, pump condition, head height, pressure, fittings, valves, and restrictions. Use measured rates for anything important.

Need the tank size or flow rate?

Use these helpers to choose a common tank, calculate volume from measurements, or estimate flow from a bucket test, then send the value back to the calculator above.

1. Choose a Known Tank

Pick a common tank-like size to get moving, then adjust the value if your actual container is different.

Common tank or pool

Common sizes are rough planning values. Prefer the label, manufacturer spec, or measured dimensions when available.

2. Calculate Your Tank Volume

Use this when you know the measurements instead of the volume. These shape helpers calculate total volume. For pools, use average water depth rather than wall height.

Only vertical cylinders are supported: round tanks or round pools. Horizontal cylinder tanks are not modeled because liquid height is not proportional to volume, partial fills and drains work differently.

Shape

Measurement unit

Length

Width

Average depth or height

2,872 U.S. gallons

Rectangular volume = length x width x height.

Send volume as

3. Estimate or Measure Flow Rate

Choose a rough rate only for planning. The better method is to time how long it takes to fill a bucket, then use that measured rate.

Common rate estimate

Typical rates vary widely. For hoses and pumps, a bucket test is usually better than a generic estimate.

Bucket Test

Fill a bucket or marked container and time it. This avoids trying to estimate flow from pipe size and pressure.

Container volume

Volume unit

Seconds to fill

6.67 U.S. gpm

Send rate as

Rain Over Area

Estimate collected rain from a simple rectangular roof, cover, patio, or catchment area. This assumes all rain reaches the tank; real runoff can be lower because of gutters, splash, first-flush diverters, leaks, or overflow.

Rain rate

Rain unit

Per

Time unit

Area measurement

Length

Width

0.164 U.S. gpm

Rain collection is an estimate. Use local rainfall data and reduce the rate if the catchment does not drain fully into the tank.

Send rate as

Saved Tanks and Rates

Save repeat tank sizes and flow rates in this browser. Local storage is convenient, but it is not a permanent record and may be cleared by browser settings.

Current tank: 10 U.S. gallons Usable tank volume from the calculator above.

Current rate: 2 U.S. gpm Fill or drain rate from the calculator above.

Tank name

Rate name

Fill and Drain History

Save calculated jobs you want to compare later, such as pool fill attempts with different hose rates.

Tank Fill and Drain Time Formula

The calculator converts tank volume and flow rate to the same base units, applies the percent level change, then divides volume by flow rate.

time = volume moved / flow rate

volume moved = tank volume x |target level - starting level| / 100

For example, a 10 U.S. gallon aquarium filled from 0% to 100% at 2 U.S. gallons per minute takes 5 minutes.

Using This Calculator

This calculator is for the practical question people usually have: how long will this tank, pool, trough, cistern, or container take to fill or drain? If you already know the volume and flow rate, use the calculator at the top. If you do not, use the tank-size and bucket-test helpers first, then send those values back into the calculator.

This is a quick estimating tool based on rough flow rates, calculated container volumes, or common tank sizes. If the job is critical, or if cost, time, overflow, damage, chemical treatment, fuel handling, or safety is a concern, measure the flow rate with the actual setup and use tools or procedures suited to that project. Many factors this calculator does not account for can change the outcome.

Treat the saved tanks, saved rates, and history as a convenience for this browser, not a permanent record. They are useful for comparing jobs or repeating common estimates, but browser storage can be cleared by settings, privacy tools, or another user of the same device.

Common Fill and Drain Rate Notes

Situation	Typical Planning Range	Use With Caution
Garden hose	About 3 to 10 U.S. gpm	Pressure, hose diameter, hose length, and fittings change the result a lot.
Bathtub or utility faucet	About 3 to 8 U.S. gpm	Aerators, valves, and plumbing restrictions matter.
Small utility or sump pump	About 10 to 60 U.S. gpm	Pump curves depend on lift height and hose losses.
Fuel dispenser	About 5 to 40 U.S. gpm	Automotive, marine, diesel, and commercial dispensers differ.
Hydrant or water truck	Hundreds of U.S. gpm	Use professional/local figures. Permits, backflow protection, and safety rules may apply.

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