Sihoo M18 Review (2026): $169.99, a Sponge Seat (Not Memory Foam), and a Fixed 17.9-Inch Seat Depth

Quick Answer: The Sihoo M18 is a budget mesh-back chair with a cushioned seat, listed at $169.99 on Sihoo’s own US store on October 29, 2026 (list $289.99), rated to 330 lb, BIFMA certified, with a 3-year warranty and 30-day returns. It gets the basics right for the price: 2D lumbar (up/down and in/out), a headrest that moves 3.9 inches and pivots 45°, and a recline to 126°. The trade-offs Sihoo’s own spec sheet confirms are a fixed 17.9-inch seat depth, height-only armrests, and a W-shaped seat made of sponge, not memory foam.

The M18 is one of the most-searched budget chairs on the market, and this site has cited it twice before, as the best-overall pick in our memory foam chair guide and the mid-range pick in our green office chair guide, without ever reviewing it on its own. Going back to the source for this review turned up two corrections to our own earlier pages, both flagged below.

The Sihoo M18 by the numbers

Per Sihoo’s US product page and spec table (checked October 29, 2026), the M18 measures 28”W x 27”D x 44”-51”H, weighs 37.1 lb, supports 330 lb, and has a 17.91-inch seat depth and 20.08-inch maximum hip width. Sihoo’s global spec page adds the numbers the US store leaves out: a seat height of 43.4-52.7 cm (about 17.1-20.7 inches), a seat width of 51 cm, lumbar travel of 4 cm in/out and 5 cm up/down, five armrest positions across 7 cm (about 2.8 inches), and a seat cushion of “premium sponge with 8.5 cm thickness” (about 3.35 inches).

On reviews, Sihoo’s own store shows 4.9 out of 5 from 2,925 reviews. Independent reviewers are less uniform: GamingTrend scored the M18 90/100 and called its recline a “fantastic 126-degree tilt”, while CGMagazine gave it 7.5/10, with a larger reviewer finding the seat “not quite deep enough for me.”

Sihoo M18 review: what you get for $169.99

Correction 1: the M18 seat is sponge, not memory foam

Search for the best office chair with memory foam and the M18 turns up again and again — including, until today, as the number-one pick in our own memory foam chair guide. Sihoo doesn’t describe it that way. The US product page says the seat is “designed in a W-shape with high-quality sponge,” the M18 FAQ on the same page calls it a “W-shaped sponge cushion,” and Sihoo’s global spec page describes “premium sponge with 8.5cm thickness.” Memory foam is a slow-recovery viscoelastic foam; the M18 never uses the term.

That matters for two reasons. A sponge (polyurethane) seat springs back right away instead of slowly molding to you, so if you want the slow sink-in feel of a memory foam mattress, the M18 won’t deliver it. And it changes how you compare: the seat thickness Sihoo actually publishes is 8.5 cm, about 3.35 inches, not the 3.15 inches our earlier page and several roundups quoted. We’ve corrected the memory foam guide to match.

Correction 2: the “2D armrests” and the seat height that isn’t there

Sihoo’s US page headlines “2D Adjustable armrests,” but its own spec table on the same page lists the armrests as “Adjustable armrests (Up and down),” and the global spec page describes five height positions. In practice they’re 1D: height only, about 2.8 inches of travel, no slide or pivot. Creative Bloq’s review noted the same thing, a long vertical range but no sideways movement.

The US spec table also lists “Chair back lifting height: 44.09” - 51.18”.” That’s the overall chair height, not the seat height. The seat height comes from Sihoo’s global spec page: 43.4-52.7 cm, or about 17.1-20.7 inches. For reference, our office chair dimensions guide puts most chairs at 16-21 inches against a standard 28-29-inch desk, so the M18 sits in the normal band, but it doesn’t go especially low for shorter sitters.

The fixed seat depth is the real fit question

The M18’s seat pan is 17.91 inches deep with no slider. Our dimensions guide uses the standard target of 2 to 4 inches between the front of the seat and the back of your knees with your back against the lumbar pad. Do that math on a fixed 17.9-inch seat and the M18 fits best if your buttock-to-knee-crease length is roughly 20 to 22 inches or more. Shorter thighs leave the seat edge pressing behind the knees, or force you to sit forward, off the lumbar pad.

It’s also why the M18 splits independent reviewers. CGMagazine’s larger reviewer found it “not quite deep enough” and said family members found it more comfortable the smaller they were, while GamingTrend’s reviewer rated it 90/100. If you’re on the shorter side, read our office chair for short people guide before buying, and look for a chair with a seat slider.

Sihoo M18 vs M57 vs Doro C300

The M18 is Sihoo’s cushioned-seat budget chair. The two Sihoo chairs it’s most often compared to fix one of its limits each, at a higher price. All prices are from Sihoo’s own US store on October 29, 2026.

Price, colors and the sale-price question

Sihoo’s US store lists the M18 at $169.99 in Black, Black with skate-style wheels, White and Blue. The list price is $289.99 for black and $299.99 for white and blue, so the roughly 41% “discount” is measured against a list price the chair rarely sells at. Treat $169.99 as the real price. Green and Pink show $299.99 and sold out on Sihoo’s store, which means a “green M18” deal on a third-party listing deserves a second look. This site has logged the M18 as low as $127.99 in a past Black Friday promotion; Black Friday 2026 falls on November 27.

Sihoo checks out on the boring things: a 3-year warranty, 30-day returns and free shipping in the US and Canada on its own store. We found no CPSC recall for any Sihoo chair in the CPSC recall database as of October 29, 2026.

Who should buy the Sihoo M18

• Buy it if you want a cushioned seat instead of mesh, a real 2D lumbar pad and a headrest for under $200.
• Buy it if your thighs are average or longer; the fixed 17.9-inch seat suits a buttock-to-knee length of about 20-22 inches or more.
• Skip it if you’re short or petite, because there’s no seat slider. Our short person guide lists chairs that adjust.
• Skip it if you want memory foam specifically. Sihoo calls the seat sponge; our memory foam chair guide has the chairs that actually name it.
• Step up to the M57 if you run hot, or the Doro C300 if you need seat-depth and 4D arm adjustment.
• Want more budget options? Our best office chair under $300 and best budget ergonomic office chair guides compare the M18’s price tier across brands.

The bottom line

The Sihoo M18 earns its popularity: at $169.99 you get a BIFMA-certified 330 lb frame, 2D lumbar, an adjustable headrest, a 126° recline and a 3-year warranty, backed by a direct-store return window. Buy it knowing what Sihoo’s own spec sheets say it isn’t: the seat is sponge rather than memory foam, the 17.9-inch seat depth doesn’t adjust, and the armrests only go up and down. If those three limits don’t affect you, it’s one of the better-documented chairs under $200.