SIHOO M18: the spec sheet, and the gap in it

The SIHOO M18 is the single most-searched individual chair in this category, so it deserves a straight answer: we cannot tell you whether it fits you, because SIHOO does not publish the figure that would.

That is not a gotcha. It is the whole review, and it is more useful than a paragraph of impressions we are not in a position to have.

That is a genuinely decent set for the price. 331 lb is above the 275 lb occupant basis behind the ANSI/BIFMA X5.1 standard, so there is real headroom for most users. A three-year warranty with free parts is longer than most of the field. And publishing a recommended user-height window at all is more than the majority of makers manage.

• A seat-height range. No floor, no ceiling, no travel span. This is the figure that decides whether the chair can put your forearms level with your desk.
• A seat depth. Which is the dimension that decides whether the front edge clears the back of your knee - and, unlike height, is almost never adjustable.
• A seat width.
• Lumbar travel. The listing names lumbar support as an adjustment without saying how far it moves.
• Which BIFMA protocol it passed. "Passed the BIFMA test" is not a protocol. X5.1 and X5.11 are different tests with different loads.

Run our fit arithmetic on SIHOO's own stated window. A 5 ft 6 in user wants a seat around 16.9 to 18.5 inches. A 6 ft 2 in user wants around 19.5 to 21.1 inches. So to serve the window SIHOO claims, the chair needs roughly 17 to 21 inches of usable range - about four inches of travel.

Four inches is a normal amount for a task chair; several chairs in our field publish exactly that. So it is entirely plausible the M18 delivers it. What we cannot do is confirm it, or tell a 5 ft 4 in user whether the floor is low enough for them - and a 5 ft 4 in user is outside the stated window anyway with nothing published to work from.

This is why the M18 is not a pick on any of our by-body roundups. Chairs for tall people ranks on published ceiling and depth; chairs for petite users ranks on published floor and depth. The M18 has neither figure, so it sits on both excluded lists. That is a consistent rule rather than a judgment on the chair.

Cost per warranty year. SIHOO publishes three years; the live price is in the card below. Divide one by the other and you have a comparable number - which is the arithmetic no competitor in our fetched set publishes, and which is available here precisely because SIHOO did publish a warranty term.

For context, the best figure on this site is about $40 per warranty year, from a chair with a five-year term. The worst is about $190, from a 700 lb chair with a one-year term. The M18 sits comfortably in the upper half of the field on this measure.

Worth flagging, because it affects what you receive. "SIHOO M18" covers several distinct listings - different wheels, headrest configurations, armrest counts and prices - and the published specifications differ between them. Some list 330 lb, some 331 lb; some name a warranty, some do not.

The card below links the specific listing this page was written from, and the price shown comes from a live lookup on that same listing. If you buy a different variant, check its own specification page: we cannot describe a listing we did not read.

If you are between 5 ft 6 in and 6 ft 2 in, the published set is reasonable for the money: capacity headroom above the X5.1 basis, a three-year parts warranty, a mesh back, four named adjustments. SIHOO has told you the band it built for, and you are in it.

If you are outside that band, buy something that publishes its range. The CAPOT in the card below answers all six of our rubric criteria - the only chair on this site that does - and the GABRYLLY publishes a 23.6-inch ceiling with a 20-inch seat depth for a tall user. Both let you check the fit before your money leaves.

And if all-day comfort is what you are actually trying to find out, we are the wrong source and we will say so rather than improvise. We have not sat in this chair. Foam behavior over months, mechanism durability, whether the lumbar lands on your curve - those need someone who owns one. Our full list of what this method cannot reach is published here.

08

The chair, and two that publish more

Ranked on the published rubric. Tap a row for the full write-up; the price button goes straight to Amazon. Every figure in the write-ups is the manufacturer's own published specification, linked at the source. We have not sat in any of these.

Scores out of 10. What the manufacturer publishes, and what it does not.

#	Product	Best for	Score	Price
1	SIHOO M18 The Chair Under Review	Users 5 ft 6 in to 6 ft 2 in	6.4★★★☆☆	$146.99 - View on Amazon #ad disclosure · September 30, 2026
2	CAPOT Ergonomic Mesh Chair The Alternative That Publishes Everything	Knowing before you buy	9.8★★★★★	$199.99 - View on Amazon #ad disclosure · September 30, 2026
3	GABRYLLY Ergonomic Mesh Office Chair The Alternative for a Tall User	A 23.6 in ceiling, 20 in deep seat	8.6★★★★½	$219.50 - View on Amazon #ad disclosure · September 30, 2026

01 · The Chair Under Review

SIHOO M18

6.4/10 ★★★☆☆ · scored on the published rubric

331 lb capacity, a three-year parts warranty and a BIFMA pass with a 1,136 kg static test - and SIHOO states the user-height window it designed for, 5 ft 6 in to 6 ft 2 in.

Why you might not: SIHOO publishes no seat-height range for the M18. That is why it is not a pick on any of our by-body roundups: we cannot tell you whether it fits you, and if you are outside that 5 ft 6 in to 6 ft 2 in window the listing gives you nothing to work with.

Published figures, from the SIHOO listing. Blank rows below are figures the manufacturer does not publish.

Rated capacity	331 lb
Warranty	3 years
Cost per warranty year	$49.00
Maker's stated user height	5 ft 6 in to 6 ft 2 in

Adjustments published (4): seat height; headrest; lumbar support; backrest angle.

Not published by the manufacturer: seat-height range; seat depth; seat width. We have flagged these rather than guessed.

How this score was built

• Fit range3/10
• Adjustability7/10
• Capacity headroom9/10
• Materials & warranty9/10
• Spec coverage4/10

The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.

$146.99 - View on Amazon

$169.99 list, 14% off

Price as of September 30, 2026. #ad how this is funded

02 · The Alternative That Publishes Everything

CAPOT Ergonomic Mesh Chair

9.8/10 ★★★★★ · scored on the published rubric

The only chair on this site that answers all six rubric criteria from published figures: seat range, depth, width, 400 lb capacity, a five-year warranty and eight levels of 2 in lumbar travel. At $199.99 that is $40 per warranty year.

Why you might not: It tops out at 22.05 in. If you are over about 6 ft 2 in you will run out of seat height, whatever the listing's stated window says.

Published figures, from the CAPOT listing. Blank rows below are figures the manufacturer does not publish.

Seat height	18.5-22.05 in
Seat depth	19.3 in
Seat width	20 in
Rated capacity	400 lb
Warranty	5 years
Cost per warranty year	$40.00
Maker's stated user height	5 ft 5 in to 6 ft 2 in

Adjustments published (5): seat height (18.5-22.05 in); lumbar depth (2 in over 8 levels); backrest lock at 90, 110 and 125 degrees; headrest height and depth; armrests flip up 90 degrees.

How this score was built

• Fit range9/10
• Adjustability10/10
• Capacity headroom10/10
• Materials & warranty10/10
• Spec coverage10/10

The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.

$199.99 - View on Amazon

Price as of September 30, 2026. #ad how this is funded

03 · The Alternative for a Tall User

GABRYLLY Ergonomic Mesh Office Chair

8.6/10 ★★★★½ · scored on the published rubric

Five of six rubric criteria answered with published figures: 18.9-23.6 in seat, 20.5 in wide, 20 in deep, 300 lb, three-year warranty. Its 23.6 in ceiling is the highest of any ordinary task chair here, which is what makes it the tall-user pick.

Why you might not: A 20 in seat depth is long. Our arithmetic says that is too deep for anyone under about 5 ft 8 in - the front edge will reach the back of your knees, which is the thing OSHA specifically tells you to avoid.

Published figures, from the GABRYLLY listing. Blank rows below are figures the manufacturer does not publish.

Seat height	18.9-23.6 in
Seat depth	20 in
Seat width	20.5 in
Rated capacity	300 lb
Warranty	3 years
Cost per warranty year	$73.17
Maker's stated user height	5 ft 2 in to 6 ft 1 in

Adjustments published (4): seat height (18.9-23.6 in); flip-up armrests (45 degrees); recline 90-120 degrees; headrest.

Not published by the manufacturer: lumbar adjustment range. We have flagged these rather than guessed.

How this score was built

• Fit range10/10
• Adjustability8/10
• Capacity headroom8/10
• Materials & warranty8/10
• Spec coverage9/10

The overall is the mean of these, rounded to one decimal place. Each criterion is computed from a published figure - the rubric is here.

$219.50 - View on Amazon

$239.50 list, 8% off

Price as of September 30, 2026. #ad how this is funded