Mammoth Performance Supersoft im Test

The Mammoth Performance Supersoft is a 27cm all-foam mattress that puts 65mm of Mammoth’s Skyfoam on top of 60mm of its Medical Grade foam and a PostureCell support core, giving the softest feel in the Performance collection. It is made in the UK, sold through stockists rather than direct, and costs from £1,199 for a single at The Sleep Shop (September 2026).

Performance Supersoft layers

Layer depths are from Mammoth’s Performance Supersoft page, which points out that Skyfoam is a separate comfort material, not a softer version of Medical Grade foam. Mammoth lists the Performance Pure with the same 27cm depth, 60mm of Medical Grade foam and PostureCell core; the Supersoft adds the 65mm Skyfoam layer.

Performance Supersoft prices by size

The Sleep Shop charges the same for the small double and the double, which makes the double the better buy if your frame takes it. Delivery is free on orders over £300.

Soft, but how soft?

The Sleep Shop rates the Supersoft medium to soft, and we place it at 4 out of 10. That suits side sleepers and lighter people who want shoulders and hips to sink in. It is also softer than the medium-firm feel the evidence favours. A systematic review of 24 trials in Sleep Health (Radwan et al., 2015) found medium-firm mattresses, ideally ones the sleeper can adjust, best for comfort, sleep quality and spinal alignment, so heavier people and front sleepers are better served by the Performance Pure or Hybrid.

Mammoth backs its foam with its own research. Mammoth’s Medical Grade foam page reports that in 2012 sleep trials run under Prof. Jason Ellis at Northumbria University’s Centre for Sleep Research, participants fell asleep 29% quicker and rated their sleep 21% more enjoyable. Those trials concerned the Medical Grade foam, not the Supersoft’s Skyfoam top, and the figures are published by Mammoth itself.

Warranty, care and safety

Mammoth’s FAQ sets out a 1-year guarantee that becomes a free 10-year warranty when you register the mattress, with full replacement for the first five years and a pro-rata share of the price after that. The mattress should be rotated head to foot every three months and never flipped. Mammoth also states compliance with the Furniture and Furnishings (Fire) (Safety) Regulations 1988, the UK law that sets ignition tests for upholstered furniture and mattress fillings.