How to Use the Pool & Tub Fill Time Calculator
If you need to step away while filling a pool or tub, knowing the fill time in advance helps you avoid an overflow. This calculator divides the volume you need to fill (in gallons) by your flow rate (GPM, gallons per minute) to estimate how long it will take.
The formula is simple: fill time (minutes) = volume (gal) รท flow rate (GPM). For example, filling a 130-gallon inflatable pool at 4 GPM takes about 33 minutes. Actual flow can vary with water pressure, hose length, kinks, and leaky connections, so treat the result as a helpful estimate rather than an exact figure.
Not sure of your flow rate? Time how many seconds it takes to fill a 1-gallon jug, then divide 60 by that number to get GPM. Water pressure can vary by time of day, so measuring at the same time you plan to fill will give a more accurate result.
A large inflatable pool typically holds 130-400 gallons, while a standard bathtub holds about 40-60 gallons. If you're running multiple hoses or faucets at once, add up their combined GPM before entering it here โ and remember that using another faucet at the same time will reduce your actual flow rate and extend the fill time.
Frequently Asked Questions
A typical faucet flows about 2-4 GPM, and a garden hose about 4-8 GPM. Time how long it takes to fill a 1-gallon container, then divide 60 by that number of seconds to estimate your GPM.
If your flow rate is cut in half, the fill time doubles. A kinked hose or old plumbing can significantly reduce flow, so it's worth checking before you start.