How long does it take to fill a pool?

Divide the volume by the flow. A 10,000 gal pool at 10 gal/min is 1,000 minutes, which is 16 h 40 min, so a hose opened at 06:00 finishes at 22:40. The flow is what moves that number: the same pool at 6 gal/min takes 1 d 3 h 47 min, and at 16 gal/min it takes 10 h 25 min. That is a whole day of difference on one pool, which is why this page asks for a flow you measured rather than a figure it picked for you.

How do I measure the flow rate of my hose?

Put a bucket of known size under the hose, open the tap the way you will leave it, and time how long the bucket takes to fill. A 5 gal bucket filled in 30 s is 10 gal/min, because 5 gal in half a minute is 10 gal in a minute. There is a stopwatch on this page for it: press start, press stop when the bucket is full, and the seconds land in the field. Mains pressure, hose length and how far the tap is open all change the answer, so the measured number beats the quoted one every time.

How many gallons does my pool hold?

Measure the pool and let the page work it out. A rectangle is length times width times average depth: 32 by 16 ft running 3 ft at the shallow end and 8 ft at the deep end averages 5.5 ft, which is 2,816 cu ft, or 21,065 gal. A round pool is pi times the radius squared times depth, so 24 ft across and 4 ft deep is 1,809.56 cu ft, or 13,536 gal. An oval is the ellipse, pi over 4 times length times width times depth, and the same 32 by 16 ft outline with the same slope comes to 16,545 gal.

Do two hoses fill a pool twice as fast?

Only if both of them really deliver what you measured on their own. The page adds simultaneous flows before it divides, so 10 and 6 gal/min is 16 gal/min and a 10,000 gal pool drops from 16 h 40 min to 10 h 25 min. Two hoses on the same supply line often share the pressure, and each one then runs slower than it did alone. If the numbers matter, time a bucket on each hose while both are running.

Why is my pool taking longer to fill than the estimate?

The arithmetic assumes the flow you measured holds steady from the first minute to the last, and very little holds steady for 16 hours. A well delivers faster than it recovers, a shared main drops when the rest of the street is awake, and a hose turned off overnight moves the finish by exactly the hours it was off. That assumption is printed beside every answer here rather than buried under it, and the fastest way to check it is to time the bucket again halfway through.

Can I use litres and metres instead of gallons and feet?

Yes, and the whole form follows the switch. A 10 by 5 m pool sloping 1.2 m to 2 m averages 1.6 m deep, which is 80 m³, or 80,000 L, and at 40 L/min that is 2,000 minutes, or 1 d 9 h 20 min. Flow can be typed as gallons a minute, gallons an hour, litres a minute, litres a second or cubic metres an hour. The conversions are exact definitions rather than rounded constants: a US gallon is 231 cubic inches, which is 3.785411784 L.

What about a kidney, a figure eight or a freeform pool?

Use I know the volume when you have a measured or documented volume for a kidney, figure-eight or other freeform pool. The geometry inputs cover a rectangle, a round pool and an ellipse, and print that shape's formula. Shallow to deep uses the average of the two end depths, which assumes an evenly sloping floor. An unsupported outline or hopper floor can make that model high or low; it has no guaranteed direction of error.

How do I estimate the time left for a partly filled pool?

Choose I know the volume and enter the amount still needed, rather than the full pool capacity. Use I know the flow or Time a bucket for the flow currently running, and set the start time for this remaining fill. The page divides that supplied remaining volume by the combined flow. It does not derive remaining volume automatically from a water-depth reading or a percentage-full estimate; interruptions and changing flow move the finish time.

Pool Fill Time Calculator

Work out how long a pool takes to fill, as a duration and a finishing time rather than a bare decimal. Type what the pool holds and the flow you measured: 10,000 gal at 10 gal/min is 1,000 minutes, which is 16 h 40 min, so a hose opened at 06:00 is done at 22:40. The flow is the number that decides everything and the one nobody knows, so fill a bucket and time it: 5 gal in 30 s is 10 gal/min, and that is your line rather than the figure on the box. A second hose adds before the division, so 10 and 6 gal/min running together is 16 gal/min and 10 h 25 min. If you do not know the volume, the page works it out from the pool: a 32 by 16 ft rectangle sloping from 3 ft to 8 ft averages 5.5 ft deep, which is 2,816 cu ft, or 21,065 gal, and 1 d 11 h 7 min at 10 gal/min. Round and oval pools have their own formulas, and every assumption the answer rests on is printed beside it.

Fill time16 h 40 min10,000 gal at 10 gal/min · 1,000 minutes · start 06:00, finish 22:40

Volume: gal
Flow: gal/min
Time: 16 h 40 min
Finish: 22:40

Volume: 10,000 gal, the figure you typed. Nothing here checks it against the pool.
Flow: 10 gal/min, held steady from the first minute to the last.
The clock runs without stopping. A pause while a well recovers, or a hose turned off overnight, moves the finish later by the length of the pause.
Finish: counted forward from 06:00 on a 24-hour clock.

The water

Type the gallons or litres the pool holds.

Volume from
Measured in

The volume goes in the first cell of the readout above, in US gallons. If you do not know it, switch to working it out from the pool and this page will size it from the measurements instead.

The flow

Type the flow the hose or the fill line delivers.

Flow from
Flow measured in

Second hose (gal/min), optional

Start time, optional

Three fills, worked through

Every number in these rows is computed by the same code the readout uses. Load one to see it in the form.

10,000 gal at 10 gal/minone hose
1,000 minutes, 16 h 40 min
Two hoses, 10 and 6 gal/minrunning together
16 gal/min, 10 h 25 min
A 5 gal bucket in 30 scalibration timer
10 gal/min

Accuracy. Exact arithmetic: volume divided by flow, with simultaneous hoses added together. It assumes the flow you measured holds steady for the whole fill, which a well or a shared main often will not, so the finish time moves with every interruption. It times a fill and gives no advice about pumps, pressure, or any limit on how much water you may draw. The volume is exact for the shape you pick: a rectangle, a round pool or an oval, with a sloping floor taken at the average of its two ends. A pool with a flat shallow section and a deep hopper, or with rounded corners, holds less than that.

Common questions

How long does it take to fill a pool?: Divide the volume by the flow. A 10,000 gal pool at 10 gal/min is 1,000 minutes, which is 16 h 40 min, so a hose opened at 06:00 finishes at 22:40. The flow is what moves that number: the same pool at 6 gal/min takes 1 d 3 h 47 min, and at 16 gal/min it takes 10 h 25 min. That is a whole day of difference on one pool, which is why this page asks for a flow you measured rather than a figure it picked for you.
How do I measure the flow rate of my hose?: Put a bucket of known size under the hose, open the tap the way you will leave it, and time how long the bucket takes to fill. A 5 gal bucket filled in 30 s is 10 gal/min, because 5 gal in half a minute is 10 gal in a minute. There is a stopwatch on this page for it: press start, press stop when the bucket is full, and the seconds land in the field. Mains pressure, hose length and how far the tap is open all change the answer, so the measured number beats the quoted one every time.
How many gallons does my pool hold?: Measure the pool and let the page work it out. A rectangle is length times width times average depth: 32 by 16 ft running 3 ft at the shallow end and 8 ft at the deep end averages 5.5 ft, which is 2,816 cu ft, or 21,065 gal. A round pool is pi times the radius squared times depth, so 24 ft across and 4 ft deep is 1,809.56 cu ft, or 13,536 gal. An oval is the ellipse, pi over 4 times length times width times depth, and the same 32 by 16 ft outline with the same slope comes to 16,545 gal.
Do two hoses fill a pool twice as fast?: Only if both of them really deliver what you measured on their own. The page adds simultaneous flows before it divides, so 10 and 6 gal/min is 16 gal/min and a 10,000 gal pool drops from 16 h 40 min to 10 h 25 min. Two hoses on the same supply line often share the pressure, and each one then runs slower than it did alone. If the numbers matter, time a bucket on each hose while both are running.
Why is my pool taking longer to fill than the estimate?: The arithmetic assumes the flow you measured holds steady from the first minute to the last, and very little holds steady for 16 hours. A well delivers faster than it recovers, a shared main drops when the rest of the street is awake, and a hose turned off overnight moves the finish by exactly the hours it was off. That assumption is printed beside every answer here rather than buried under it, and the fastest way to check it is to time the bucket again halfway through.
Can I use litres and metres instead of gallons and feet?: Yes, and the whole form follows the switch. A 10 by 5 m pool sloping 1.2 m to 2 m averages 1.6 m deep, which is 80 m³, or 80,000 L, and at 40 L/min that is 2,000 minutes, or 1 d 9 h 20 min. Flow can be typed as gallons a minute, gallons an hour, litres a minute, litres a second or cubic metres an hour. The conversions are exact definitions rather than rounded constants: a US gallon is 231 cubic inches, which is 3.785411784 L.
What about a kidney, a figure eight or a freeform pool?: Use I know the volume when you have a measured or documented volume for a kidney, figure-eight or other freeform pool. The geometry inputs cover a rectangle, a round pool and an ellipse, and print that shape's formula. Shallow to deep uses the average of the two end depths, which assumes an evenly sloping floor. An unsupported outline or hopper floor can make that model high or low; it has no guaranteed direction of error.
How do I estimate the time left for a partly filled pool?: Choose I know the volume and enter the amount still needed, rather than the full pool capacity. Use I know the flow or Time a bucket for the flow currently running, and set the start time for this remaining fill. The page divides that supplied remaining volume by the combined flow. It does not derive remaining volume automatically from a water-depth reading or a percentage-full estimate; interruptions and changing flow move the finish time.

Exact arithmetic: volume divided by flow, with simultaneous hoses added together. It assumes the flow you measured holds steady for the whole fill, which a well or a shared main often will not, so the finish time moves with every interruption. It times a fill and gives no advice about pumps, pressure, or any limit on how much water you may draw.