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Guide

Inflatable hot tub sizes and water volumes

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In short

Most inflatable hot tubs are between about 155 and 230 cm across and 65 to 80 cm tall. Four seat tubs usually hold around 600 to 800 litres, six seat tubs around 800 to 1,200 litres. Leave at least a walkway round the tub plus room for the pump unit, and check the inner size, not just the outer, for legroom.

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Hot tub sizes on listings can be confusing. Outer sizes include the thick inflatable wall, so the space you sit in is much smaller. Seat counts assume people sitting close together. Water volume is sometimes given in litres, sometimes in US gallons. This guide brings the numbers together in one chart using models from our guides, explains how to read them and shows how much space to allow on your patio.

Size chart for common models

These figures come from the Amazon UK listings of tubs in our guides. UK gallons are litres divided by 4.546. Where a listing does not give a figure, it is marked not stated.

ModelOuter sizeWaterUK gallonsSeats
Wave Pacific 4 person155 x 155 x 65 cmNot statedNot stated4
MSpa Tidal173 x 173 x 65 cm930 LAbout 2056
Lay-Z-Spa 60001180 cm, 66 cm high669 LAbout 1474
Lay-Z-Spa Hawaii HydroJet Pro180 x 180 x 71 cm795 LAbout 1756
MSpa Denver180 x 180 x 70 cm970 LAbout 2136
Wave Como Eco Foam195 x 195 x 70 cmNot statedNot stated6
Lay-Z-Spa Milan AirJet Plus196 x 71 cm916 LAbout 2016
Bestway Santorini HydroJet Pro216 x 216 x 80 cm1,190 LAbout 2625 to 7
Outer size, water and seats from the listings

Compare 6 person tubs →

Outer size, inner size and legroom

The wall of an inflatable tub is thick, often 20 cm or more on each side. So a tub with a 196 cm outer diameter may have an inner diameter of only around 150 cm. Few listings give the inner size, so check the manual or measure inside the wall before you rely on the seat count.

Legroom depends on the inner size. On a round tub, people sit around the edge with their feet towards the middle, so a larger inner diameter matters more than the seat count. Square tubs of the same width have about 27% more floor area, which gives more room in the corners. See round vs square for the sums.

inner 145 cmabout 660 Linner 145 cmabout 840 Lround, 200 cm outersquare, 200 cm outer
Same outer width and inner width, but the square tub holds more water and has more seating in the corners. Water depth 40 cm.

Seats on the listing vs real comfort

Seat counts assume people sitting shoulder to shoulder. As a rough guide, a tub sold for four suits two or three adults in comfort, and a six seater suits four adults or a family with children. If you often have guests, go up a size.

Our 2 to 4 person guide covers smaller tubs and the 6 person guide covers family sizes.

Working out water volume

If a listing does not give litres, you can work it out from the inner size and water depth. For a round tub, litres equal pi times the inner radius squared times the depth, all in centimetres, divided by 1,000. For a square tub, multiply inner length by width by depth and divide by 1,000. Our water volume calculator does the sums and also gives fill time from your hose flow.

Some listings give US gallons. One US gallon is about 3.785 litres, so 290 US gallons is about 1,100 litres. A UK gallon is larger, at about 4.546 litres.

  1. 1

    Measure the inner diameter or inner length and width.

  2. 2

    Find the water depth at the fill line in the manual.

  3. 3

    Use the formula or calculator to get litres.

  4. 4

    Use litres to plan chemical doses, heating time and base load.

How much space to leave

Allow the outer size plus room to walk round at least part of the tub, room for the pump unit beside it and space to lift the cover off and lay it down. Keep the pump within reach of the socket without an extension lead. Leave access to the drain valve, and keep the tub clear of fences, sheds and overhanging branches.

The base must also take the filled weight. Water weighs about 1 kg per litre, so a 916 litre tub holds about 916 kg of water before the tub and people. See base ideas for how to check the load.

Note:Keep the tub within reach of an RCD protected outdoor socket so you do not need an extension lead, and always supervise children around the tub.

Frequently asked questions

What is a standard inflatable hot tub size? Many are about 180 to 196 cm across and 66 to 71 cm tall.

How many litres is a 4 person hot tub? The Lay-Z-Spa 60001 holds 669 litres. Other four seat tubs vary, so check the listing.

How many gallons is an inflatable hot tub? A 916 litre tub holds about 201 UK gallons or about 242 US gallons.

How much space do I need? The outer size plus a walkway, room for the pump and space for the cover.

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