Hot tub filled weight calculator
A hot tub is light empty and very heavy full, because water weighs 8.34 lb per gallon. Enter your gallons, the tub's empty weight, and how many people use it to get the loaded total. This is the number your deck, pad, or balcony has to hold.
Not sure? Look up your model or use the volume calculator.
From your tub's spec. Typically 600 to 1,000 lb for an acrylic tub, 50 to 90 lb for an inflatable.
Counted at about 185 lb each.
Enter your gallons for the weight.
The math
Water weighs 8.34 lb per US gallon, so the water alone in a 400 gallon tub is about 3,340 lb. Add the tub's empty weight (often 600 to 1,000 lb for an acrylic shell) and the people (about 185 lb each), and a full mid-size tub commonly lands between 4,000 and 5,500 lb loaded. A ground-level concrete pad handles that easily; a raised deck or balcony usually needs to be checked, and sometimes reinforced, against its rated load. When in doubt, ask a contractor.
Common questions
Can my deck hold a hot tub?
A typical residential deck is built for about 50 lb per square foot, and a loaded hot tub often exceeds that over its footprint. Many decks can take a tub, but a raised or older deck should be checked by a contractor and may need extra footings or beams. A ground-level concrete or paver pad is the safe default.
How much does the water alone weigh?
Multiply gallons by 8.34. A 300 gallon tub holds about 2,500 lb of water; a 500 gallon tub about 4,170 lb. That water weight is usually the largest part of the loaded total and the part you can compute exactly.
Where do I find my tub's empty weight?
On the manufacturer spec sheet, listed as dry weight or weight (empty). For many popular models it is also on that model's page here under sizes. If you cannot find it, leave it blank and the calculator shows the water and people weight, which is most of the load.