Quick answer
Fill time = pool volume ÷ flow rate. A 15,000 gallon pool filled at 10 gallons per minute takes 1,500 minutes, which is 25 hours or about 1.04 days.
Enter the pool volume and the hose flow rate. The calculator returns hours and days.
Related tools: Appliance Energy Cost Calculator: Electricity cost of running an appliance. Wall Area Calculator: Wall area of a rectangular room after openings. Water Usage Calculator: Household water use from people and use per person.
How to use the Pool Fill Time Calculator
- Enter pool volume (gal) (above 0).
- Enter flow rate (gal/min) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Pool volume | A number, in gal | > 0 |
| Flow rate | A number, in gal/min | > 0 |
Formula and method
Formula
time = volume ÷ flow rate
IEEE-754 double precision; shown to the decimals indicated.
Measure your hose flow by timing how long it takes to fill a bucket.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Pool volume = 15000; Flow rate = 10.
| Result | Value |
|---|---|
| Fill time | 25 hours |
| In days | 1.04 |
Example 2
Inputs: Pool volume = 24000; Flow rate = 15.
| Result | Value |
|---|---|
| Fill time | 26.7 hours |
| In days | 1.11 |
Example 3
Inputs: Pool volume = 500; Flow rate = 5.
| Result | Value |
|---|---|
| Fill time | 1.7 hours |
| In days | 0.07 |
The first line is the headline result (fill time). Below it the pool Fill Time Calculator lists in days, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Measuring flow
Time how long it takes to fill a 5-gallon bucket: if it takes 30 seconds, the flow is 10 gallons per minute. A typical garden hose delivers 5 to 12 gallons per minute depending on pressure and diameter.
Pool volume
For a rectangular pool, volume in gallons is length × width × average depth × 7.48. Use the average of the shallow and deep ends for sloped pools. Using two hoses at once cuts the time roughly in half if your supply can keep up.
How the result changes with pool volume
Holding every other input at the first worked example, this table changes only pool volume. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Pool volume | Fill time | In days |
|---|---|---|
| 7500 | 12.5 hours | 0.52 |
| 15000 | 25 hours | 1.04 |
| 30000 | 50 hours | 2.08 |
| 60000 | 100 hours | 4.17 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Pool volume: entering "0" shows "Pool volume must be greater than 0." beside that field and no result.
- Flow rate: entering "0" shows "Flow rate must be greater than 0." beside that field and no result.
Choosing between the Pool Fill Time Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Appliance Energy Cost Calculator](/lifestyle/appliance-energy-cost-calculator/) | power, hours used per day and electricity price | Cost per day |
| [Wall Area Calculator](/lifestyle/wall-area-calculator/) | room length, room width and ceiling height | Wall area |
| [Water Usage Calculator](/lifestyle/water-usage-calculator/) | people, water per person per day and days | Water used |
| [Lighting Lumens Calculator](/lifestyle/lighting-lumens-calculator/) | room area and target light level | Lumens needed |
| [Room Area Calculator](/lifestyle/room-area-calculator/) | length and width | Room area |
Assumptions and limitations
- Flow can drop at low supply pressure
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for pool volume and flow rate to confirm this.
Frequently asked questions
How much does it cost to fill?
Multiply gallons by your water rate; see the water bill calculator.
Can the hose pressure change?
Yes, flow drops with other water use.
Should I fill while away?
It is safer to stay close, because hoses can slip out and an unattended pool can overflow.
What does the Pool Fill Time Calculator calculate?
Hours to fill a pool at a flow rate. It returns Fill time and In days.
What formula does the Pool Fill Time Calculator use?
time = volume ÷ flow rate. Measure your hose flow by timing how long it takes to fill a bucket.
What do I need to enter in the pool Fill Time Calculator?
You enter Pool volume (gal) and Flow rate (gal/min).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Flow can drop at low supply pressure.
What is an example of a pool Fill Time result?
With pool volume 15000 and flow rate 10, the fill time is 25 hours.
Related calculators
- Appliance Energy Cost Calculator — Electricity cost of running an appliance.
- Wall Area Calculator — Wall area of a rectangular room after openings.
- Water Usage Calculator — Household water use from people and use per person.
- Lighting Lumens Calculator — Lumens needed for a room at a light level you choose.
- Room Area Calculator — Floor area of a rectangular room.
- Water Bill Calculator — Water bill from usage, rate and a base charge you enter.
Sources
- ISO 8601-1: Date and time, representations for information interchange (calendar dates, ordinal dates and week dates)
- Gregorian calendar reform, papal bull Inter gravissimas (1582): the leap-year rule used for all dates
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.