SIHOO M56C vs SIHOO M18: Which Should You Buy?

Key difference: The M56C lists about $110 lower, but the M18 is rated for more weight.

What follows compares the M56C and M18 on SIHOO's own specifications and regular US list prices, not on a Chairpedia test.

Why compare them

Why put the SIHOO M56C next to the SIHOO M18? The M56C and the M18 are two of SIHOO's lower-priced chairs with a headrest, and first-time buyers often weigh one against the other.

Specs side by side

Strengths and weaknesses

SIHOO M56C

Strengths

• Lower list price: from $184.99 against $289.99 for the M18.
• Automatic lumbar support ("Ultra-wide dynamic lumbar support: a flexible elastic plate that moves with the backrest (no manual adjustment listed)"), where the M18's is set by hand.

Good to know

• Check the weight rating: 300 lb (≈136 kg), against 330 lb (≈150 kg) on the M18.
• If you lean far back, note it reclines up to 125°, against 126° on the M18.

SIHOO M18

Strengths

• Higher maximum load: 330 lb (≈150 kg), against 300 lb (≈136 kg) on the M56C.
• Deeper recline: up to 126° against 125° on the M56C.

Good to know

• Compare the list prices first: it starts at $289.99, against $184.99 for the M56C.
• Plan a minute to set the lumbar by hand ("Lumbar support adjusts vertically and horizontally"); the M56C's moves on its own.

How they differ

Price. At regular US list prices the SIHOO M56C is $184.99 and the SIHOO M18 is $289.99–$299.99. The M56C lists about $110 below the M18, before any store sale. Price options: the M56C — Black $184.99; the M18 — Black (incl. Skate Wheels) $289.99; White/Blue/Green/Pink $299.99.

Lumbar support. The SIHOO M56C lists “Ultra-wide dynamic lumbar support: a flexible elastic plate that moves with the backrest (no manual adjustment listed)”, the SIHOO M18 “Lumbar support adjusts vertically and horizontally”. The M56C's lumbar moves on its own as you shift, while the M18's is positioned by hand.

Maximum load. The SIHOO M56C lists “300 lb (≈136 kg)”, the SIHOO M18 “330 lb (≈150 kg)”. The M18 is rated for more weight than the M56C.

Recline. The SIHOO M56C lists “Up to 125°; 1 lock position”, the SIHOO M18 “Up to 126°”. The M18 leans back further than the M56C.

Seat size. Seat width: the SIHOO M56C lists “≈20.1 in (51 cm)”, the SIHOO M18 nothing. Seat depth: the SIHOO M56C lists “17.1 in (≈43.4 cm)”, the SIHOO M18 “17.91 in (≈45.5 cm)”.

Other details. For the M56C and M18, the table above gives the armrests, headrest and chair weight in each brand's own wording.

Same on both. The M56C and M18 list the same warranty (3 years).

Who should buy which

• Pick the M56C over the M18 if you want the lower price — the M56C lists about $110 below the M18.
• Pick the M56C over the M18 if you want lumbar support that adjusts itself as you move, with nothing to set.
• Pick the M18 over the M56C if you want a higher weight rating: 330 lb (≈150 kg).
• Pick the M18 over the M56C if you want a deeper recline (up to 126°).

Not published by the brand (M56C vs M18): seat height for the SIHOO M56C; seat height and seat width for the SIHOO M18.

Sources

• SIHOO M56C (compared here with the M18): Sihoo M56C Ergonomic Office Chair - Full Back Support with Cotton Seat Cushion – Official US Sihoo Store; Sihoo M56C Ergonomic Chair | Dual-Section Backrest & Comfort – UK Sihoo official Shop, checked 2026-10-13; US list price from SIHOO US Official Store, checked 2026-10-13.
• SIHOO M18 (compared here with the M56C): Sihoo M18 Ergonomic Office Chair – Official US Sihoo Store, checked 2026-09-29; US list price from SIHOO US Official Store, checked 2026-10-07.
• Figures marked ≈ for the M56C and M18 are Chairpedia's unit conversions, not brand figures.