Guide
How much does a hot tub weigh when full?
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In short
An empty inflatable hot tub usually weighs about 30 to 40 kg, but water weighs about 1 kg per litre, so a 916 litre tub weighs roughly 950 kg filled and well over a tonne with four adults in it. That load sits on a footprint of about 3 square metres. Put it on a level, firm base that can take it, and get advice for decks or upper floors.
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Hot tub weight is easy to underestimate. In the box, an inflatable tub is light enough for two people to carry. Fill it with water and add a few bathers, and it becomes one of the heaviest things in the garden. Knowing the figure helps you choose a safe base, decide whether decking is suitable and plan an indoor spot. This guide shows how to work out the weight for any tub, with examples for common sizes.
Empty weight
Inflatable tubs are light when empty. The Lay-Z-Spa Milan and Honolulu listings in our guides both give 38 kg for the tub. The pump unit and cover add a little. Hard shell tubs are far heavier empty, often hundreds of kilograms.
Empty weight matters for carrying and storage, but it is tiny compared with the water.
Water weight
One litre of water weighs about 1 kg. So a tub's water weight in kilograms is roughly its capacity in litres. A 669 litre tub holds about 669 kg of water; a 1,190 litre tub holds about 1,190 kg. Use our water volume calculator if you only know the inner size.
- Level concrete slab
- Decking: check it is rated for the load
- Compacted, level gravel with a mat
Adding it up
The table adds empty weight, water and an example of four bathers at 75 kg each. Bather weights are only an example; use your own figures.
| Tub capacity | Approx. empty tub | Water | Four bathers (example) | Approx. total |
|---|---|---|---|---|
| 669 L | About 30 to 40 kg | About 669 kg | 300 kg | About 1,000 kg |
| 916 L | 38 kg (listing) | About 916 kg | 300 kg | About 1,250 kg |
| 1,190 L | Check listing | About 1,190 kg | 300 kg | About 1,500 kg plus tub |
Load per square metre
Divide the total by the footprint. A 196 cm round tub covers about 3 square metres, so 1,250 kg works out at roughly 400 kg per square metre. A square tub spreads the load over a larger area for the same outer width.
That is a heavy, even load. A level concrete slab or well laid paving usually copes. Decking needs to be designed for it, and lawns can sink unevenly. See base ideas.
Decks, balconies and indoor floors
Garden decks are often built for people and furniture, not a tonne or more of water in one spot. Before placing a tub on decking, check the joists, posts and footings, or ask a builder or structural engineer. Balconies and upper floors need professional advice in every case.
If you want a tub indoors, read can you put an inflatable hot tub indoors.
Note:Never place a filled hot tub on a balcony, roof or upper floor without a structural engineer confirming the load. Overloaded structures can fail without warning.
Choosing a size with weight in mind
If your base is limited, a smaller tub reduces the load. A 2 to 4 person tub holds much less water than a 6 to 8 person model. Compare capacities in our 2 to 4 person guide and 6 to 8 person guide, and see inflatable hot tub sizes.
Why the base must be level as well as strong
Weight is only half the story. An uneven base puts extra strain on one side of the wall and the seams, and water finds its own level, so the tub looks lopsided and the fill line is wrong. Even a slight slope is worth correcting before you fill.
On paving, check with a long spirit level in several directions. On a lawn, the ground can settle under a tonne of water over a few weeks, so a slab, compacted sub base or a purpose built platform is a better long term choice. Add an insulating ground mat on top; it also protects the floor of the tub from sharp grit.
When you drain the tub, remember the same weight of water has to go somewhere. See how to drain an inflatable hot tub for safe draining.
Frequently asked questions
How much does an empty inflatable hot tub weigh? Usually around 30 to 40 kg for the tub. The Lay-Z-Spa Milan listing gives 38 kg.
How heavy is a full Lay-Z-Spa? A 916 litre model weighs roughly 950 kg filled, before bathers.
Can I put a hot tub on decking? Only if the deck is built to carry the load. Check with a builder or structural engineer.
How heavy is a hot tub cover? Inflatable lids are light; foam lids are heavier and get heavier if they absorb water.
What you need
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Lay-Z-Spa 60001: 4 seats and 669 L
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MSpa Tidal: semi-rigid 6 seater, 930 L