Sihoo M57 vs Sihoo M18: 30-Day Ergonomic Lab Test Comparison

Evaluated by: Ryan Miller, Ergonomic Hardware Specialist
Evaluation Scope: 30-Day Side-by-Side Office Evaluation (Daily Workstation Use)
Focus Areas: Seat-surface thermal observations, armrest mobility for desk work, lumbar positioning, and workspace clearance.

Sihoo M57 vs M18: Which Ergonomic Office Chair Is Better? (2026 Comparison)

The Short Answer: The Sihoo M57 is our preferred choice for computer-intensive desk work because its full-mesh seat allows passive air circulation, its 3D armrests provide multi-axis forearm positioning for typing and mouse use, and its cast aluminum base provides a rigid foundation. The Sihoo M18 is the better option if you prefer the soft initial feel of traditional foam cushioning, frequently sit with one leg folded, or want a simpler configuration with fewer moving adjustment points.

Manufacturer Specifications vs. Our Physical Measurements

To avoid confusion between official marketing data and practical fit, the table below separates manufacturer-listed specifications from our physical measurements and observations:

M57 vs M18: The 5 Differences That Actually Matter

1. Seat Pan: Suspension Mesh vs. Molded Foam

The seat pan is the most consequential structural difference between the two chairs:

• Sihoo M57 (Full Mesh): The woven mesh allows open air circulation beneath the seat, making it noticeably cooler in warm environments. The suspension provides a firm, buoyant feel when sitting upright. However, keeping mesh in tension requires a rigid outer composite frame. If you sit with your legs spread wide, your outer thighs may contact the hard plastic rim. For a standalone evaluation of mesh elasticity, see our full Sihoo M57 review.
• Sihoo M18 (Molded Foam): The high-density foam cushion provides immediate, familiar softness with no hard edges around the perimeter. The trade-off is thermal retention: foam naturally retains body heat during continuous sessions, and the woven fabric cover collects dust and pet hair more easily than mesh. To read our detailed assessment of the foam seat, see our Sihoo M18 review.

2. Armrests: 3D Mobility vs. Height-Adjustable

Armrest versatility is a primary differentiator for typing and desk tasks:

• Sihoo M57 (3D Armrests): You can rotate the pads inward to support your forearms while typing on compact keyboards, or slide them backward to pull closer to shallow desks without lowering the seat height.
• Sihoo M18 (Height Adjustable): Adjusts vertically only. If you work at a standard desk and keep your arms stationary, these basic adjustments may be entirely adequate.

3. Lumbar Adjustment Mechanics

Both chairs feature Sihoo’s rear-mounted rotary lumbar module that adjusts vertically and horizontally. On the M57, forward depth travel provides direct contact because the mesh does not compress. On the M18, the dial pushes further forward to reach the lower back through cushion compression. For more lumbar-focused options, see our guide to the best ergonomic office chairs for lower back pain.

4. Headrest Range & Base Construction

Both chairs offer height- and angle-adjustable headrests (mesh on M57, foam-padded on M18). In terms of base construction, the M57 uses a polished cast aluminum star base that resists scuffs, whereas the M18 relies on welded chrome-plated steel.

5. Posture & Leg Positioning

The M18’s padded perimeter makes it more accommodating for casual sitting postures, such as folding one leg under the thigh. On the M57, the rigid outer perimeter frame holding the mesh taut limits lateral leg spread.

Desk Clearance & Workspace Compatibility

How each chair interacts with standard 28-to-30-inch home office desks:

What Neither Chair Does Well

• No Seat Depth Adjustment: Neither chair has a sliding seat pan mechanism. Thigh support is fixed to the physical frame dimensions.
• Fixed Backrest Height: While the lumbar pad moves independently, the main backrest frame cannot be raised or lowered to match different torso lengths.
• Basic Recline Locking: Both models use a 3-step recline lock rather than an infinite smooth-angle tilt limiter found on premium chairs.

Who Should Buy Each Chair?

Is the Sihoo M57 Worth the Upgrade Over the M18?

To evaluate whether the M57 justifies choosing it over the M18, we recommend using this practical decision rule:

• Choose the M57 if you are a full-time computer worker who values 3D armrest adjustability and breathable mesh for all-day typing and mouse tasks.
• Choose the M18 if your budget is the primary priority, or if you specifically prefer the soft contour of traditional foam over suspended mesh.

Testing Methodology & Limitations

Both chairs were evaluated in a standard home office environment over a 30-day period. Our assessment focused on physical measurements and repeatable daily observations:

• Measurement Protocol: Usable seat dimensions, armrest adjustments, and lumbar travel were recorded using digital calipers and tape measures.
• Thermal Observation: Surface heat distribution patterns were documented using thermal imaging after 3-hour continuous sitting sessions at an ambient room temperature of 72°F (22°C). Peak seat surface temperature reached ~78.4°F on the M57 mesh compared to ~86.5°F on the M18 foam cushion under our test conditions.
• Desk Compatibility: Both chairs were tested under standard 28-to-30-inch desks to evaluate pull-in clearance, armrest height fit, and caster mobility.

What We Did NOT Test: This review does not include multi-year longitudinal durability testing, robotic cyclic fatigue load tests beyond 30 days, or clinical medical outcomes.

Final Verdict

Frequently Asked Questions: Sihoo M57 vs Sihoo M18