WalkingPad X21 Review: The Folding Treadmill That Actually Disappears

The WalkingPad X21 is KingSmith's flagship folding treadmill and the answer to a very specific British problem: wanting a treadmill while living somewhere with no room for one. Most "folding" treadmills fold the deck up and still leave you with a large, heavy object taking up a corner. The X21 folds the deck in half and then folds again, ending up roughly 101cm tall by 71cm wide by 23cm thick, which genuinely stands behind a door or slides under a bed.

At around £630 on Amazon UK it is not cheap for what it does, and there are compromises that follow directly from the folding mechanism. But if the alternative is not owning a treadmill at all, the X21 is one of the few machines that solves the actual problem rather than pretending to.

Who it is for

The X21 is for someone in a flat, a small house or a shared space who wants to walk or jog indoors and has nowhere to leave a machine standing. It is also a strong option for anyone who wants steady walking volume, whether that is hitting a step target on a rainy week or building the 150 minutes of moderate activity the NHS recommends across the week alongside strength work on at least two days. Regular brisk walking is unglamorous and remarkably effective, and the biggest predictor of whether people do it indoors is whether the machine is easy to get out.

It is the wrong machine for three groups. Anyone over 110kg is excluded outright by the weight limit. Anyone who wants to do proper running training will find the belt too short and the frame too light. And anyone who has space for a conventional treadmill will get more machine per pound elsewhere, which our best treadmill under £1000 guide covers.

The folding mechanism

This is the reason the X21 exists, so it deserves the first look. The running deck hinges in the middle and folds back on itself, then the whole assembly folds down at the base. Stored, it is around 101 x 71 x 23cm, which is thin enough to stand upright in a wardrobe, behind a sofa or against a wall without dominating a room.

Two wheels at the base mean you can tip it and roll it, and at 37kg net it is manageable for one reasonably able person, though it is not light. The mechanism itself feels well engineered rather than flimsy, with proper catches, and it is the part of the machine that has attracted the least criticism from owners over several years on sale.

The honest trade-off is that everything else on the treadmill is compromised in service of this. The deck has to be thin, so cushioning is minimal. The frame has to be light, so the weight limit is 110kg. There is no room for an incline motor, so there is no incline. None of these are faults in the engineering. They are the price of the folding, and you should decide whether the folding is worth them before anything else.

Specifications as published by WalkingPad UK at the time of writing.

Performance and the horsepower question

Worth addressing head on: the listing quotes 918W, and the manufacturer's own page describes a 3.75 HP brushless motor. Those two figures do not reconcile. 918W is roughly 1.2 HP of actual continuous draw, and 3.75 HP is a peak marketing figure of the kind that is common across the whole treadmill industry. This is not KingSmith being uniquely dishonest, it is a category-wide habit, but you should read the real number as a bit over 1 HP and set your expectations accordingly.

In practice that means it is comfortable and quiet for walking at any speed, perfectly happy at a brisk 6 to 7km/h, and working noticeably harder if you are a heavier user jogging at 10km/h or more. It is a walking machine that can jog rather than a running machine that can walk.

The 121 x 46cm belt is the X21's real advantage over cheaper walking pads, which commonly give you 100 x 40cm or less. That extra width and length makes a genuine difference to how relaxed you feel at pace, because you are not constantly conscious of where the edges are. It is still short for running: a natural running stride at 12km/h wants closer to 140 to 150cm, so faster efforts feel cramped and you end up shortening your stride.

The rotary dial on the handrail is a small design decision that gets a lot of praise from owners, and rightly so. Changing speed by turning a knob under your hand is quicker and less disruptive than hunting for buttons, particularly when you are walking and working at the same time.

Living with it

Setup is genuinely nothing. It arrives assembled, you unfold it, plug it in and walk. That is a real advantage over conventional treadmills, which frequently need two people and an hour.

Noise is low at walking speeds, which matters if you live above someone. It gets louder as you speed up, and the deck is thin enough that footfall carries more than it would on a heavily cushioned machine. A rubber mat underneath is a worthwhile addition for both noise and floor protection.

Cushioning is the other daily compromise. On a 30 minute walk you will not think about it. On an hour of walking or repeated jogging sessions, the firmness of a thin folding deck becomes noticeable, particularly through the knees. If you have joint issues, this is the specification to weigh most carefully.

The KS Fit app connects over Bluetooth, logs sessions and adds a few modes and firmware updates. It works, it is not essential, and the treadmill functions completely normally without it.

Value

At roughly £630, the X21 costs about what a decent conventional folding treadmill with incline and a 140cm belt costs. On paper that comparison goes badly for the X21, because you get less belt, less power, no incline and a lower weight limit.

The comparison only makes sense if you weight storage properly. A conventional folding treadmill needs a permanent home. The X21 does not, and for a lot of UK households that is the difference between a treadmill that gets used and a treadmill that never gets bought. If you are choosing between the X21 and no treadmill, it is good value. If you are choosing between the X21 and a machine you have room to leave out, the conventional treadmill wins on almost every specification.

Against KingSmith's own cheaper pads it is a clear step up. The WalkingPad C2 is a walking-only machine with a narrower belt and a 6km/h top speed. The X21 costs considerably more and gives you the width, the speed and a handrail, which is the right upgrade for anyone who wants to do more than stroll. There is more context in our best walking pad UK guide and the wider treadmills section. Consistent walking of this kind is one of the most reliable ways to protect heart health over the long term (British Heart Foundation on physical activity).

Check price on Amazon

Recommended reads

1. The best walking pad in the UK
2. KingSmith WalkingPad C2 review
3. The best fold flat treadmill in the UK
4. The best home treadmill for walking
5. Treadmill reviews and buying guides