Last seen for £349 at Mattress Man on 10th November 2026
Silentnight Miracoil Sleep King Size Mattress
The Silentnight Miracoil Sleep Mattress is a medium firm sprung mattress built around Silentnight's Miracoil spring system, which means a supportive, slightly firmer feel that suits back and front sleepers well.
- Suits back & front sleepers
- Support spread across the mattress
- Easy care, only needs rotating
Save with the previous model
Some retailers still sell the earlier version of this mattress for less than the current model's best price.
More available sizes
Last seen for £299 at Mattress Man on 27th October 2026
Last seen for £349 at Mattress Man on 10th November 2026
Last seen for £425 at Mattress Man on 27th October 2026
Last seen for £299 at Mattress Man on 10th November 2026
Last seen for £229 at Mattress Man on 10th November 2026
Mattress details
Mattress
Silentnight Miracoil Sleep Mattress
Size
Firmness
Medium Firm
Construction
Open Coil Spring
Depth (cm)
Layers
Layer Details
Key benefits
- 75cm each for two sharing: You each get 75cm of width, which means propping up with a book or turning over without elbowing anyone.
- Extra length for taller sleepers: At 200cm, the UK king is 10cm longer than the UK double, a genuine relief if one of you is nearing six foot.
- Space that softens partner disturbance: The Miracoil spring system already keeps movement fairly localised, and the wider footprint means a restless partner is simply further away.
- A firmer feel that rewards room to spread: Medium firm support suits back and front sleepers, and the added width lets you find your position rather than compromise on someone else's.
- An affordable route into the size: King is where many couples land, and this mattress keeps the step up from a double within reach; compare the retailers listed on this page for live prices.
This size suits you if...
You share the bed every night and a double has started to feel cramped, especially if one of you gets up hours before the other and you'd rather not feel every movement. It also suits couples where one partner is approaching six foot and keeps finding their feet at the edge of a 190cm mattress. Allow at least 2.7m x 2.9m of bedroom, with 3.2m x 3.2m comfortable.
Consider another size if...
Your bedroom is under our suggested 2.7m x 2.9m minimum, or you sleep alone. We'd recommend the UK double instead, which is 15cm narrower and needs at least 2.6m x 2.8m of room.
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FAQ's
Is the Silentnight Miracoil worth getting in a UK king for couples?
For most couples, yes. The UK king gives you 75cm of width each, and combined with the Miracoil system's fairly localised movement, one person shifting or getting up early is far less disruptive than on a double. Lightweight side sleepers may still find the medium firm feel a little unyielding, whatever the size.
What room size do I need for the Silentnight Miracoil in a UK king?
We suggest at least 2.7m x 2.9m, with 3.2m x 3.2m feeling comfortable. That allows walking space on both sides and room to open drawers. Newer homes can be tighter than they first appear once wardrobes go in, so measure the usable floor rather than the room on the plan.
Is the UK king Silentnight Miracoil long enough for someone over six foot?
It's the most sensible size in the range for taller sleepers. At 200cm, the UK king is 10cm longer than the UK double, which is usually enough to stop feet hanging off the end for anyone around the six foot mark. Only the UK super king matches that length.
How much bigger is this mattress in a UK king than in a double?
The UK king is 15cm wider and 10cm longer than the UK double, taking you from 135 x 190cm to 150 x 200cm. That works out at 75cm of width each for two people sharing, a difference you notice every night rather than a marginal upgrade on paper.
Should I size up to the super king instead?
If your room stretches to at least 3m x 2.9m and you want maximum separation, perhaps with a dog who claims a share of the bed, the UK super king adds 30cm of width at the same length. In most bedrooms the UK king is the better balance of space and practicality.