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Round is the traditional shape for an inflatable spa, and the physics backs it up. Air pressure pushes evenly on a circular wall, so there are no corners to bulge, crease or strain the seams. The result is a firmer edge to lean against and a tub that keeps its shape over several seasons.
It also changes how a soak feels. In a circle everyone faces the middle, so conversation is easy and nobody is stuck shoulder to shoulder along one side. A round lid has no corners to lift in the wind either, so it sits flat and seals the water surface, which is where a hot tub loses most of its heat.
A circle covers less ground than a square of the same width. A 180cm round hot tub takes up about 2.5m², while a 180cm square one takes 3.2m², so the round version uses roughly a fifth less patio. That leaves space for steps, a side table or a path round the edge.
| Round | Square | |
|---|---|---|
| Seating | Everyone faces the middle | Two to a side, a straight back to lean on |
| Floor area at 180cm wide | About 2.5m² | About 3.2m² |
| Inflatable wall | Even pressure all round | Corners take extra strain |
| Best spot | Open patio, middle of a deck, walk-round access | Tucked into a corner or against a fence |
| Lid fit | No corners to seal | Corners can lift in wind |
If your only space is a corner between two fences, a square tub uses it better. Anywhere you can walk around the tub, the circle usually wins.
Circular spas are sold by outside diameter, but an inflatable wall is thick, so the space inside is far smaller than the box suggests. The Lay-Z-Spa St Lucia is 170cm across and 124cm inside, the Lay-Z-Spa Miami 180cm and 132cm, and the Dellonda DL90 175cm and 135cm. Seat counts are the most that fit, not the most that fit comfortably, so knock one off if you want to stretch your legs.
Two or three adults, or two adults and a child. The St Lucia and Aruba are 170cm PVC circles; the foam-wall Carrara (170cm) and Wave Tahoe (156cm) are rated for four to six by their makers, so check the inside size before buying one for a family.
The most common size. The Miami, Boracay and Dellonda are 175-180cm and suit two to four. The 208cm Aoxun holds 1,000 litres for four adults.
The 196cm Palm Springs AirJet 6, Coleman Palm Springs and New York seat four to six, the 208cm Nordivale four to six, and the 236cm Intex PureSpa Bubble 8 is the biggest circle we stock. For more family-size tubs in every shape, see our six-seat inflatable spas.
Figures come from each tub's listing. Prices change daily on Amazon, so we show the band each one sat in when we checked.
| Model | Diameter | Seats | Water | Jets | Wall | Price band |
|---|---|---|---|---|---|---|
| Wave Tahoe | 156cm | 4-6 | - | 90 AquaJets | 6-inch foam core | Over £750 |
| Lay-Z-Spa St Lucia | 170cm (124cm inside) | 2-3 | 605L | 110 | 3-layer PVC, I-beam | Under £500 |
| Lay-Z-Spa Aruba | 170cm | 3 | 800L | 110 | 3-layer PVC | Under £500 |
| Lay-Z-Spa Carrara | 170cm | 4-6 | - | 140 | ThermaCore foam | £500-£750 |
| Dellonda DL90 | 175cm (135cm inside) | 2-4 | 800L | 110 | Rattan-effect PVC | Under £400 |
| Lay-Z-Spa Miami | 180cm (132cm inside) | 2-4 | 669L | 120 | TriTech 3-layer | Under £400 |
| Lay-Z-Spa Boracay Smart | 180cm | 4 | 669L | 120 | 3-layer DuraPlus | Under £400 |
| Lay-Z-Spa Helsinki AirJet Plus | 180cm | Up to 7 | - | 180 | Drop stitch | £500-£750 |
| Lay-Z-Spa Palm Springs AirJet 6 | 196cm | 4-6 | - | 140 | PVC | Under £400 |
| Lay-Z-Spa New York | 196cm | 6 | About 1,200L | 140 | TriTech 3-layer | Under £500 |
| Coleman Palm Springs | 196cm | 4-6 | - | 140 | DuraPlus 3-layer | Over £750 |
| Aoxun | 208cm | 4 | 1,000L | 130 | 3-layer PVC | Under £400 |
| Nordivale | 208cm | 4-6 | - | 130 | 0.66mm PVC, mesh | Under £300 |
| Intex PureSpa Bubble 8 | 236cm | 8 | 1,340L | 170 | Fiber-Tech beams | £500-£750 |
Jet counts on bubble spas are holes in a ring round the floor, not separate nozzles, so 110 and 140 feel much the same. The bigger differences are the wall, the insulation and how many people really fit.
At 180cm with a 132cm interior, the Miami gives two people plenty of room and four a snug soak. Its 669 litres heat at about 1.5-2°C an hour, the lid and top cover come in the box and the pump has Freeze Shield. It sat under £400 when we checked, which makes it the easy default.
Both are 170cm. The St Lucia holds 605 litres, the least of any tub here, so it is the quickest to heat. The Aruba holds 800 litres in the same footprint and weighs only 26.3kg empty, with a 1.5kW heater and an RCD on the plug. For other compact shapes see our 2 seater spas.
Same 180cm, 669-litre size as the Miami, plus Wi-Fi control, two jet intensity levels, a reinforced locking cover and a built-in RCD. Allow 2.5 hours to fill and 12-24 hours for the first heat, which you can start from your phone.
The Helsinki's FortiFiber drop stitch wall inflates far firmer than standard PVC and stands more upright. It has 180 AirJets, a 2,200W heater and a wood-effect finish; more timber-look tubs are in our wood effect spas.
Foam walls swap air for an insulated core. Wave says the Tahoe's 6-inch PU foam keeps heat 60% better than a standard PVC tub, and Lay-Z-Spa rates the Carrara's ThermaCore wall 60% more efficient. They cost more to buy but less to keep warm through a British winter.
The Intex is 236cm across and holds 1,340 litres for up to eight, with 170 bubble jets and hard water treatment built in. The 208cm Nordivale is the cheapest round tub we stock, under £300 when we checked, with 130 jets and four filter cartridges in the box. For more on that price band see our cheapest hot tubs.
A circle is the easiest shape to build in all three. Standard 3-layer PVC, held in shape by internal beams (I-beam, Fiber-Tech, MaxHold), is light, packs small and is the cheapest, which is why most round tubs under £500 use it. The wall flexes a little when you lean back.
Drop stitch links the inner and outer skins with thousands of threads, so it inflates firmer and sits upright. Foam walls such as the Tahoe's are the most insulating but the heaviest to move and store.
Plan for a circle plus a margin of 30-50cm for getting in and out, the lid and the pump, which sits outside the wall. A 180cm tub then needs a clear, level square of about 2.6m; Aoxun asks for at least 250 x 250cm for its 208cm model.
Water weighs 1kg a litre. The Miami with 669 litres, its own 32kg and two adults comes to about 850kg spread over 2.5m², or roughly 330kg per square metre. The Intex 8 with eight adults is nearer two tonnes over 4.4m². Paving or a concrete pad is ideal; have a builder check older decking, and never put a tub on a balcony without a structural engineer's say-so. Lawn sinks unevenly and kills the grass.
These tubs run from a standard 13A plug, most with an RCD or GFCI built into the plug or pump, and heat to 40°C. The heaters are 1.5-2.2kW, so warming from cold is slow: the St Lucia and Miami quote 1.5-2°C an hour, the Intex 8 0.8-1.5°C. Raising 669 litres from 10°C to 38°C takes about 22kWh before any heat loss, which is why Lay-Z-Spa allows 12-24 hours for a first heat. Multiply by your tariff, or the Ofgem price cap rate, to see the cost.
Inflatable circular spas measure 156-236cm across the outside and 65-71cm high. Inside is much smaller: a 170cm St Lucia is 124cm across.
About two to three at 170cm, two to four at 180cm, four to six at 196-208cm and up to eight at 236cm. The figure on the box is a maximum.
For an open patio, round: it uses about a fifth less floor area at the same width, everyone faces each other and the inflatable wall holds its shape better. A square tub fits a corner better.
In our range, the 156cm Wave Tahoe by outside size and the 605-litre St Lucia by water volume.
Yes, eight in our range: the St Lucia, Aruba, Carrara, Miami, Boracay, Helsinki, Palm Springs AirJet 6 and New York. Lay-Z-Spa is Bestway's brand, which also makes the Coleman Palm Springs.
Yes. They run on a standard 13A plug, most with an RCD or GFCI built in. Use an outdoor weatherproof socket and no extension lead.
RoSPA advises no under-fives, sessions of about 15 minutes, constant supervision and a lockable cover. Keep the sanitiser topped up and change filters as the manual says; the HSE spa pool guidance explains the legionella risk.
When we checked, from under £300 for the 208cm Nordivale to over £1,000 for the foam-wall Wave Tahoe. Six round tubs were under £400 (see all our inflatable hot tubs under £400) and three more under £500.
