The WalkingPad X21 is worth considering if you want a foldable treadmill that reaches 7.5 mph, but it is not the best fit for every small apartment. It folds upright for storage and has an 18.1-inch-wide running surface. However, its 81 lb weight and space needs make it less convenient to move and use in some homes.

The key question is not how thin the X21 folds. It is whether you have enough room to use it and store it when your workout is over.

This review looks at the X21’s verified specifications, motor claims, noise information, storage design and ownership costs. It also compares the X21 with other WalkingPad models to help you choose the right option.

What are the WalkingPad X21’s specifications?

The WalkingPad X21 is a double-fold treadmill made by Beijing Kingsmith Technology. The U.S. product page identifies it as the X21 (X212). A regional KINGSMITH manual identifies the machine as TRX21F.

There is an important difference between these sources. The regional manual lists a 220–240V model, while the U.S. product page lists 110V. The manual helps explain the treadmill’s design, but its electrical details should not be treated as U.S. specifications.

Here is what the U.S. manufacturer currently lists.

The X21 belongs to WalkingPad’s Running Series. Its 7.5 mph maximum speed gives it more speed options than the brand’s basic under-desk walking models.

However, one specification needs closer attention: the motor rating.

What does the X21’s 3.75 HP motor rating mean?

WalkingPad advertises a 3.75 HP brushless motor on its U.S. product page. However, the page does not say whether this is rated or peak horsepower.

The Australian manufacturer page gives more detail. It lists the X21 with:

• 1.25 HP rated motor output.
• 3.75 HP peak motor output.

The regional TRX21F manual also lists 918W rated power for its 220–240V model.

These figures come from manufacturer documents for different markets. They do not confirm the continuous motor output of the U.S. 110V model.

For this review, we report 3.75 HP as the figure advertised on the U.S. product page. We do not treat it as verified continuous output.

Sources: WalkingPad U.S. specifications · WalkingPad Australia specifications · KINGSMITH TRX21F manual.

Is the WalkingPad X21 practical for small apartments?

The X21’s main space-saving feature is its ability to fold upright.

When open, it measures 55.8 inches long, 27.9 inches wide and 41.4 inches high. When folded, it measures 39.6 × 27.9 × 8.8 inches.

That makes it much thinner in storage. But it does not mean the treadmill needs very little room during use.

How much floor space does the X21 need?

The unfolded treadmill occupies about 10.8 square feet. This is the machine’s footprint alone, without any space around it.

The regional KINGSMITH TRX21F manual specifies more than 500 mm of clearance on each side and more than 2,000 mm behind the treadmill. Its safety diagram shows the rear space as an area for moving away from the treadmill if needed. [SAFETY REVIEW: Confirm the purpose and required clearances against the exact U.S. model instructions before publication.]

These measurements come from a 220–240V regional manual, not a separately verified U.S. manual.

For illustration, combining those clearances with the U.S. product dimensions gives this approximate planning area:

This is an important difference for apartment buyers.

The treadmill itself takes up less than 11 square feet when open. However, the space needed around it can be much larger.

Measure your workout area before ordering. Do not choose the X21 based on its folded dimensions alone.

How much space does the X21 save when folded?

The X21 folds to just 8.8 inches thick. This gives you an upright storage option instead of leaving the treadmill open all day.

Possible storage locations include:

• An unused part of a multipurpose room.
• A dedicated home gym corner.
• A suitable space against a wall.
• A storage area with enough room to access the machine.

The X21 weighs 81 lb, so its thin folded shape does not make it a lightweight treadmill.

WalkingPad lists transport wheels that allow the folded machine to be moved across a suitable surface. Rolling it across a level floor is different from carrying it upstairs.

Apartment-fit verdict: The X21 makes more sense when you have a clear workout area and a suitable place to store it. It is less suitable when every part of your apartment needs to serve several purposes.

What workouts can the WalkingPad X21 handle?

The X21 has a published speed range of 1–7.5 mph, or about 1.6–12.1 km/h.

WalkingPad places it in its Running Series. Its U.S. product page also describes it as suitable for walking and jogging.

However, the maximum speed does not tell you whether the running surface will suit your stride.

The running surface measures 47.6 × 18.1 inches.

Its width is greater than the WalkingPad C2’s listed 15.7-inch walking area. However, the X21 still has a compact deck compared with many full-size treadmills.

If you normally use a larger treadmill, compare these dimensions with your preferred stride before buying.

Does the WalkingPad X21 have an incline?

The current U.S. product specification table does not list an incline adjustment.

You should not buy the X21 expecting a confirmed incline feature.

WalkingPad offers incline options on selected other models, but features can vary by model and region.

If incline is important to your workouts, ask the seller to confirm the exact model’s features before ordering.

Is the WalkingPad X21 quiet enough for an apartment?

WalkingPad advertises noise below 65 dB on its U.S. product page.

The regional TRX21F manual gives a more specific figure: below 65 dB at 8 km/h under no-load conditions. This means the measurement is not a normal workout test with a person walking on the treadmill.

The U.S. product page does not state the same test conditions.

WalkingPad’s official FAQ says that noise can vary with speed, user weight, flooring and maintenance.

For apartment buyers, there are two types of noise to consider:

Motor and mechanical noise: Sound from the motor and moving parts.

Footstep and floor noise: Sound and vibration created when someone walks or runs on the deck. Some of this sound may travel through the floor.

A no-load noise measurement does not tell you how much sound your neighbors will hear.

This matters in apartments with light floors or bedrooms directly below the workout area.

Check the floor type, treadmill position and manufacturer’s setup instructions before buying. Do not treat the advertised noise figure as a promise that the X21 will be inaudible to other people.

How practical is the X21’s double-fold design?

The X21 folds into an upright position rather than simply folding its deck in half.

WalkingPad also lists transport wheels, which allow the folded treadmill to be moved across a suitable surface.

Three details are worth considering.

Weight: The X21 weighs 81 lb. The C2 has a listed net weight of 55 lb, so the X21 is the heavier machine. This matters if you plan to move your treadmill between rooms or floors.If portability is a higher priority than running speed, the C2 is worth considering. It has a lower listed net weight of 55 lb compared with the X21’s 81 lb. Read our WalkingPad C2 review for a closer look at its dimensions, folding design and suitability for smaller homes.

Storage access: The folded dimensions help only if you have a suitable place to store the machine.

Setup: WalkingPad lists the X21 as fully assembled. You do not need to build its frame, but you still need to unfold it, connect the power cord, install the phone holder and pair the app as described in the manual.

Fully assembled does not mean no setup is needed.

What controls and app features does the X21 offer?

The X21 combines a physical speed control with app features.

How does SpeedDial work?

SpeedDial is the physical knob used to adjust the treadmill’s speed.

It gives you a way to control the machine without relying only on your phone.

Does the X21 work with the KS Fit app?

Yes. The X21 supports the KS Fit companion app.

The manufacturer also lists Apple Watch compatibility through KS Fit connected to an iPhone. Check current app availability and device compatibility before buying, especially if you use an older phone or watch.

Does the WalkingPad X21 include a remote?

No. The U.S. specification page does not list a separate remote.

The listed controls are SpeedDial and the KS Fit app. The X21 also lists NFC for app connection.

This setup may suit buyers who prefer a physical control on the treadmill. However, it may not suit someone who specifically wants a handheld remote.

How does the WalkingPad X21 compare with other models?

The X21 is not automatically the best WalkingPad for every buyer. The main choice is between a running-series treadmill and a walking-focused model.

WalkingPad X21 vs C2: Which should you choose?

The C2 is designed for walking and has a published maximum speed of 4 mph. The X21 reaches 7.5 mph and belongs to WalkingPad’s Running Series.

If your main goal is desk walking or adding light movement to your workday, the WalkingPad C2 review explains its dimensions, walking performance, storage design and limitations in more detail. For buyers who also want jogging and faster workouts, the X21 offers a wider speed range.

WalkingPad X21 vs A1 Pro: Which is better for desk walking?

The A1 Pro is another walking-focused model that WalkingPad includes among its everyday walking and home-office options.

It is worth comparing when walking, rather than running, is your main goal.

The X21 offers a higher maximum speed, but it is also an 81 lb running-series treadmill. These models serve different needs.

WalkingPad X21 vs X214: Is the faster model worth considering?

The X214 offers a higher maximum speed and foldable side handrails.

The X214 may be worth comparing if you need its higher speed or side handrails. However, its listed net weight is 14.2 lb more than the X21.

WalkingPad X21 vs X218: Which has better specifications?

The X218 has a higher published speed and weight capacity.

The X218 is worth considering if you need its higher speed or weight capacity.

The X21 is 48 lb lighter, but has lower published limits. Your choice depends on which specifications matter to your workouts and home.

What are the WalkingPad X21’s main advantages and limitations?

What are the advantages?

• Upright storage: The double-fold design reduces the treadmill’s storage thickness to 8.8 inches.
• Higher speed range: Its 7.5 mph maximum is above the C2’s 4 mph limit.
• 18.1-inch running surface: Wider than the C2’s listed 15.7-inch walking area.
• Fully assembled: The manufacturer does not require you to build the treadmill frame.
• Physical speed control: SpeedDial works alongside the app.
• App connectivity: KS Fit and Apple Watch compatibility are listed by the manufacturer.

What are the limitations?

• Non-adjustable handrail: The handrail cannot be adjusted.
• No listed incline adjustment: The U.S. product page does not list this feature.
• 81 lb net weight: Moving and carrying the treadmill needs planning.
• No separate remote: Controls are through SpeedDial and the app.
• 7.5 mph speed limit: It may not suit people who need a faster treadmill.
• Operating-space requirements: The treadmill’s footprint does not include the space around it.
• Unclear motor rating: Regional manufacturer documents give different details about rated and peak output.

Is the WalkingPad X21 worth $699?

During the November 12, 2026 price check, WalkingPad’s U.S. product page listed the X21 at $699 against a displayed reference price of $999.

That is a displayed discount of $300. The price is a dated snapshot, not a promise that the promotion will remain available.

Check the latest WalkingPad X21 price and availability.

Before buying, also check the warranty and the cost of returning the treadmill.

What warranty does the WalkingPad X21 have?

WalkingPad’s U.S. policy lists a one-year limited warranty for products bought directly from WalkingPad.com. The warranty is subject to the manufacturer’s terms.

Purchases through other retailers may have different seller and warranty conditions.

See the official WalkingPad policy before ordering.

What does it cost to return the X21?

Eligible direct purchases from WalkingPad.com can be returned within 30 days of delivery. Returns require approval and must meet the manufacturer’s conditions.

For change-of-mind returns, the customer is responsible for return shipping.

WalkingPad’s current policy gives an estimated prepaid return shipping cost starting at $120 or more for selected models, including the X21. This is not a fixed charge for every return. The final cost depends on the package, shipping distance and carrier rates.

For an 81 lb treadmill, that is an important cost to consider.

Measure your space and check the return policy before ordering. It is better to find out that the treadmill does not fit before delivery.

Who should buy the WalkingPad X21?

The X21 is worth considering if you want a running-series treadmill that folds upright between workouts.

It is a better match for buyers who:

• Want more than basic under-desk walking.
• Need a maximum published speed of 7.5 mph.
• Have enough room for the treadmill when open.
• Can accommodate an 81 lb machine.
• Have a suitable place for upright storage.
• Do not need an incline adjustment.

It is less suitable if your main goal is simply adding walking to your home-office routine.

Who should avoid the WalkingPad X21?

Consider another model if:

• You mainly want to walk while working at a desk.
• Your workout area cannot fit the treadmill and its required clearances.
• You need a lighter machine that is easier to carry upstairs.
• You require incline training.
• You regularly run faster than 7.5 mph.
• You prefer adjustable handrails.
• You need a higher user-weight capacity.

For desk walking, compare the WalkingPad C2 and A1 Pro. For higher speed or weight capacity, investigate the X214 and X218.

You can also explore our guides to the best under-desk treadmills and the best walking pads for apartments.

What should you know before buying the WalkingPad X21?

Can the WalkingPad X21 be stored vertically?

Yes. Its double-fold design supports upright storage. WalkingPad lists folded dimensions of 39.6 × 27.9 × 8.8 inches. Follow the storage instructions supplied with your exact model.

Is the WalkingPad X21 suitable for running?

WalkingPad places the X21 in its Running Series and lists a maximum speed of 7.5 mph with a 47.6 × 18.1-inch running surface. Its U.S. description also mentions walking and jogging. Whether the deck suits your running style depends on your stride and preferred pace. This review does not claim hands-on running tests.

Does the WalkingPad X21 have an incline?

The current U.S. product specification table does not list an incline adjustment. Contact WalkingPad or the seller if incline is important to your purchase.

Can you use the WalkingPad X21 under a standing desk?

It would not be my first choice for conventional under-desk walking. Its non-adjustable handrail and Running Series design make the C2 or A1 Pro more relevant alternatives.

How much does the WalkingPad X21 weigh?

The U.S. manufacturer lists a net weight of 81 lb and a gross shipping weight of 92 lb.

Does the WalkingPad X21 come assembled?

Yes. WalkingPad lists it as fully assembled. You still need to unfold it and complete the setup steps in the manual.

Is the WalkingPad X21 quiet?

The regional TRX21F manual lists noise below 65 dB at 8 km/h under no-load conditions. The U.S. product page also advertises noise below 65 dB but does not give the same test details. Neither figure is an independent measurement during a normal workout.

Does the WalkingPad X21 include a remote?

No. Its listed control options are the SpeedDial knob and KS Fit app.

What is the WalkingPad X21’s weight capacity?

The U.S. individual product page lists a maximum user weight of 240 lb. The manufacturer’s comparison guide displays 243 lb, so this review uses the individual product-page figure.

What warranty does the WalkingPad X21 have?

WalkingPad lists a one-year limited warranty for products bought directly from WalkingPad.com, subject to its terms.

Should you buy the WalkingPad X21?

The WalkingPad X21 makes sense if you want more speed than a basic walking pad and have a suitable place to store an 81 lb treadmill upright.

Its double-fold design helps with storage, but it does not remove the need for space during a workout. The non-adjustable handrail, lack of a listed incline adjustment and 7.5 mph speed limit also matter when comparing models.

For desk walking, start with the C2 or A1 Pro. For higher speed or weight capacity, compare the X214 or X218.

Our recommendation: Choose the X21 only after checking three things: whether its speed range fits your workouts, whether your room can fit the treadmill and its required clearances, and whether you can manage its weight and return conditions.

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About this review

SmallSpaceStrength publishes research-based home fitness buying guides. Product specifications are checked against available manufacturer information, and independent testing observations are attributed to their original sources. We do not claim hands-on testing where none has been performed.