KingSmith WalkingPad TRX21F Folding Treadmill

Full‑size treadmills can feel overwhelming in small flats, especially if you want both walking and light running without a huge frame or constant noise. The KingSmith WalkingPad TRX21F folding treadmill (WalkingPad X21 series) uses a compact deck, double‑fold frame and brushless motor to deliver a comfortable stride and quiet performance while still offering up to around 12 km/h for home workouts.

This guide looks at how the TRX21F fits into flats and shared homes, focusing on noise, speed range, folding format and day-to-day practicality.

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For current pricing and availability, see the WalkingPad TRX21F on Amazon UK or Amazon US.

QuietFit Lab Snapshot

Noise level: Not tested by QuietFit Lab. Listings describe a brushless motor and a shock-absorbing deck. One US listing claims 75 dB, which is a seller claim.

Apartment‑friendly: Space-saving: The deck folds upright for storage.

Vibration level: Not tested. Depends on the floor and setup.

Small‑space fit: The double-fold frame stands upright for storage, and the manufacturer states it takes up less than 0.16 m² of floor space.

Best for: Users who want quiet walking and light running with a more “real treadmill” feel in a small home.

Not ideal for: People who only need a flat under‑desk pad or require very high‑speed running.

Overall, the TRX21F is built as a compact, quiet treadmill that bridges the gap between basic walking pads and bulky gym treadmills, giving flats and small homes a more capable belt without taking over the room.

Key features and specs

UK and US listings for the TRX21F / WalkingPad X21 show slightly different wording and numbers, so QuietFit Lab uses overlapping ranges from both sites rather than a single figure. Use these unless your specific retailer page lists slightly different specs.

Speed range around 1–12 km/h (about 1–7.5 mph), covering gentle walking through to light running.

Brushless motor Brushless motor listed at up to 2 HP. Power figures vary by source: the manual lists 918 W, UK Amazon shows 1.25 HP input power, and the US Amazon listing shows "110 watts", which does not match the manual. Check the figure on your retailer's listing.

Maximum user weight Maximum user weight: UK listings and the manufacturer give 110 kg (about 242 lb). The US Amazon listing shows 100 kg and 242 lb in one table and 240 lb in an image. Confirm on your listing.

Running belt length around 121 cm / 47.6" and width about 46 cm / 18.1", designed for a comfortable walking and jogging stride in a compact footprint.

Deck height roughly 9.6 cm / 3.78", which helps reduce step height and minimise trip risk.

Double fold frame: the deck folds up in two steps into a vertical position. The manufacturer calls it double-fold, though the US Amazon listing describes it as "tri-fold vertical storage".

Integrated handlebar with HD LED display showing speed, time, distance and calories, plus detachable phone/tablet holder.

Rotational dial speed control on the handlebar for quick, intuitive speed changes while walking or running.

App connectivity (KS Fit app) for logging workouts and setting child‑lock or speed limits, with Bluetooth connectivity mentioned on some US listings.

Emergency stop cable and safety key, included in the package.

Noise and “quiet factor”

Both UK and US product descriptions emphasise the TRX21F’s quiet brushless motor and shock‑absorbing running board, presenting it as suitable for home workouts without excessive mechanical noise. The low deck height, cushioned EVA board and multi‑layer belt are aimed at reducing impact sounds as well as vibration through the frame.

QuietFit Lab has not tested this treadmill for noise, so we cannot say how loud it will be in your home. Noise will depend on speed, user weight, the floor and how the machine is set up. The manufacturer's descriptions mention a brushless motor and a shock-absorbing deck, and one US Amazon listing claims 75 dB. That figure is a seller claim, and we have not verified it. As with any motorised treadmill, a treadmill mat is a sensible extra step on hard floors or in upstairs rooms, but it does not guarantee a particular noise level.

QuietFit Lab uses affiliate links.If you buy through the links on this page, we may earn a small commission at no extra cost to you. This helps support the site and keeps our reviews independent. As an Amazon Associate, QuietFit Lab earns from qualifying purchases.

Under‑desk and small‑space use

The TRX21F is a compact treadmill with a full handle frame, not a pure under‑desk walking pad, so it best suits small rooms where you can dedicate a patch of floor to a “real treadmill” feel. The double-fold vertical storage design is intended to minimise footprint when not in use, freeing up living‑room or office space between workouts.

Folded upright, the X21 series occupies around 0.16 m² of floor area with a compact height of roughly 100 cm. That means it can live against a wall or in a corner more easily than a conventional treadmill, while still rolling out for comfortable walking and jogging sessions on a 47.6" belt when you want to train.

Comfort, stability and safety

Product information highlights a 46 cm / 18.1" wide belt and cushioned running board aimed at a stable, spacious feel for both walking and running. The relatively low deck height helps reduce the feeling of stepping up onto the machine, which can make getting on and off safer and more intuitive for home users.

The integrated handlebar and rotary dial control give a simple, tactile way to manage speed without complex touchscreens, while the HD LED display and tablet holder support longer sessions with entertainment or app‑based guidance. Safety features like the emergency stop cable and child lock (via the KS Fit app) add extra reassurance for households sharing the treadmill.

Pros

Brushless motor with shock‑absorbing running board, designed for home use.

Speed range up to around 12 km/h / 7.5 mph for walking and light running.

Double-fold frame with vertical storage that saves floor space in small rooms.

Wide belt and comfortable deck length compared with many basic walking pads.

Simple rotary dial control and HD LED display, plus tablet holder and app connectivity.

Cons

Not a pure under‑desk pad: full handle frame and belt height make it better for stand‑alone treadmill use.

Price point is higher than many basic walking pads, reflecting the wider belt and folding frame.

Maximum user weight (around 100–110 kg) may feel limiting for heavier runners.

Requires a suitable wall area for vertical storage; may not suit very cramped or irregular spaces.

As with most folding treadmills, belt length remains shorter than high‑end gym machines, which some tall users may notice at top speeds.

Who the KingSmith WalkingPad TRX21F is best for

The TRX21F is likely to suit:

Apartment dwellers who want a compact treadmill for regular walking and light running.

Home users who value easier vertical storage and a clean, minimal design over large console treadmills.

People who prefer simple dial‑based controls and tablet‑driven workouts rather than built‑in screens.

Users who want more belt width and comfort than basic flat walking pads but still need a small‑space footprint.

It is less likely to suit:

Heavy runners wanting long belts for fast intervals.

Users who need ultra‑low‑cost under‑desk pads.

Anyone whose space cannot accommodate vertical storage against a wall.

Where To Buy

KingSmith / WalkingPad’s official online store and regional distributors.

Amazon.co.uk, under names like “WalkingPad Folding Treadmill for Heavy People with Handle & Large Area” and model TRX21F.

Check the latest price for the KingSmith WalkingPad TRX21F on Amazon UK

Check the latest price for the KingSmith WalkingPad TRX21F on Amazon US

Always check the product name (TRX21F / WalkingPad X21), listed belt size, maximum user weight and warranty details before buying, as WalkingPad also sells other X‑series treadmills and walking pads with different frames and performance levels.