Use your tub’s spec sheet if you have it. Otherwise measure inside: round tubs π × (diameter ÷ 2)² × water depth, square tubs length × width × water depth. Acrylic tubs with seats hold much less than the box they fit in.
177gal
Bestway Lay-Z-Spa Miami AirJet (2–4 person)
About 669 L4 people
Save this test and get a reminder before your next soak.
Spa Calc for iPhoneComing soon to the App StoreInflatable capacities are usually stated at the fill line, often 80% of the brim. The models listed here show where each figure comes from. Confirm against your manual or the box.
Hot tubs hold so little water that a 20% error in volume is a 20% error in every dose, which in a 300 gallon tub can be the difference between 4 and 5 ppm.
Most hold 200 to 500 gallons. Inflatables are usually 175 to 300 gallons.