Hot Tub Water Volume Calculator
Calculate the water volume of your hot tub or spa based on its shape and dimensions.
Results in gallons and liters.
Water Volume
Hot tub volume depends on shape and dimensions.
Round tub:
Volume = π × radius² × depth × 7.48 (gallons per cubic foot)
Square/Rectangular tub:
Volume = length × width × depth × 7.48
Oval tub:
Volume = π × (length/2) × (width/2) × depth × 7.48
When using centimeters, the calculator converts to feet first (1 cm = 0.0328 feet), computes volume, then converts to gallons and liters.
When using inches, each dimension is divided by 12 to get feet.
Multiply by 80% since hot tubs have seats and contours that reduce the actual water volume.
Typical hot tub volumes:
- 2-person: 150–220 gallons (570–830 liters)
- 4-person: 250–350 gallons (950–1,325 liters)
- 6-person: 350–475 gallons (1,325–1,800 liters)
- 8-person: 475–700 gallons (1,800–2,650 liters)
1 gallon = 3.785 liters. 1 cubic foot = 7.48 gallons.