Office chairs

How Should an Office Chair Recline (Synchro-Tilt, Knee-Tilt, Tilt Lock)?

Published · By Ergocrew · Specs and guidance as of that date, from the pages under Sources

Summary

Look for a recline you can move into and hold, with controls that suit your use. OSHA asks for at least 15 degrees from vertical and a backrest that locks or has tension adjustment. Synchro-tilt and knee-tilt describe movement, while a tilt lock restricts it. Compare the actual range, holding positions and resistance controls; a mechanism name alone does not establish fit or compliance.

What the backrest should do when you lean back

OSHA's chair guidance names two requirements. The first is a recline adjustment of "at least 15 degrees from the vertical." The second is a backrest that should "lock in place or be tension adjustable." A backrest that tips back freely, with no lock and no resistance to set, fails the second.

OSHA's page on neutral working postures describes a reclined sitting position with the torso and neck "between 105 and 120 degrees from the thighs." That angle is measured between your torso and your thighs. A chair listing may measure its angle from a different reference, so the two numbers cannot be compared directly. Before you buy, ask the seller what the stated angle is measured from: the seat, the floor or the vertical.

CCOHS, Canada's occupational health agency, says in its chair guidance that a workstation should allow "for voluntary changes in the working position." That gives you a reason to try the transition as well as the fully reclined position.

Synchro-tilt, knee-tilt and other mechanisms

HON's chair-function guidance distinguishes movement geometry from the controls that resist or stop it. The terms below explain those differences; a Sihoo or ProtoArc model still needs its own specification check.

A brand name does not say which of these types a chair uses, so if the pivot point is not given, ask the seller whether the seat moves with the backrest and by how much.

Tilt tension and tilt lock

Tension sets how hard the backrest pushes back. Usually you turn a knob under the seat until the backrest neither throws you forward nor drops away when you lean. Set it while seated, following the model's instructions, so you can lean back and return without a sudden drop or an excessive push forward.

Some mechanisms adapt resistance to the sitter. Sihoo uses "Weight-Adaptive" for the B300 Pro and "weight-responsive" for the Doro C300 Pro V2; neither term alone tells you whether a manual override is available. If you are much lighter or heavier than average, ask the seller how the chair handles weights outside its usual range and whether you can make any manual adjustment.

A tilt lock restricts tilt, but the available positions differ: some controls lock upright, some provide several stops, and others allow a position within a range. Ask which positions the actual model holds. OSHA's wording accepts either a lock or tension adjustment, and a chair can offer both.

Recline ranges the makers list

The recline figures below are quoted as each maker writes them. Prices are as read at each maker's store on 2026-10-13.

ModelMechanism as the maker names itRecline as the maker states itPrice, store and date
Sihoo B300 ProWeight-Adaptive Recline105° / 120° / 135°, three lockable anglesfrom $259.99 at Sihoo's US store, checked 2026-10-13
Sihoo Doro C300 Pro V2Weight-responsive recline; confirm mechanismthree positions: 105°, 120°, 135°from $429.99 at Sihoo's US store, checked 2026-10-13
ProtoArc Flexer ProAuto-sync recline95° to 130°, four lock positions: 95°/105°/115°/130°$209.99 at ProtoArc's US store, checked 2026-10-13
Sihoo M18Confirm mechanism with Sihoomaximum 126° recline anglefrom $169.99 at Sihoo's US store, checked 2026-10-13

The Flexer Pro's listed span is 130 - 95 = 35 degrees across four stops. The B300 Pro's is 135 - 105 = 30 degrees across three. Those spans do not establish which chair fits you better, especially if their reference angles differ. If you want an intermediate position, check the lock spacing and try the movement. For the M18, ask Sihoo for the start angle and locking positions before comparing its maximum with a multi-stop chair.

If you want a lock between upright and fully back, the Flexer Pro lists stops at 105° and 115° for $209.99 at ProtoArc's US store, checked 2026-10-13. The B300 Pro's middle stop is 120°, from $259.99 at Sihoo's US store, checked 2026-10-13.

Prices on the Sihoo listings differ by color or version, which is why they read "from." At Sihoo's US store, checked 2026-10-13, the Doro C300 Pro V2 Black Standard Version was $429.99 and its Black Footrest Version $469.99: $469.99 - $429.99 = $40.

What to check on a listing

Our guide to the office chair features that matter for long workdays covers these other parts in more detail.

Browsing for one? Browse chairs in the feed →

Related guides

Sources

  1. HON, 2018 Seating Pricer, Seating Functions page 19
  2. OSHA Computer Workstations eTool, Chairs
  3. OSHA Computer Workstations eTool, Neutral Working Postures
  4. CCOHS, Office Ergonomics - Adjusting the Chair
  5. Sihoo, B300 Pro Ergonomic Office Chair
  6. Sihoo, Doro C300 Pro V2 Ergonomic Office Chair
  7. Sihoo, M18 Ergonomic Chair
  8. Sihoo, Doro S300 Ergonomic Chair
  9. ProtoArc, Flexer Pro Ergonomic Chair

We have not tested these products. Specs and guidance are as published on these pages on the date above and can change; the manufacturer's page for your model has the current details.

More office chairs guides

Office chairsWhat Should You Look for When Choosing an Office Chair?An office chair has to fit two things at once, your body and the desk you already own. Compare the seat-height range, seat depth and seat width first…Read the guide →Office chairsWhat Makes an Office Chair Ergonomic?An ergonomic office chair fits your body and desk through adjustable seat height, seat depth, back support and armrests. The label alone does not…Read the guide →Office chairsWhat Order Should You Use to Adjust an Office Chair?Start at the floor and work up: seat height, then seat depth and the backrest, then the armrests, and only then the monitor and the things you reach…Read the guide →Office chairsWhere Should Lumbar Support Sit on an Office Chair?Lumbar support should meet the inward curve of your lower back while you sit back with your feet supported. Its position depends on your body and the…Read the guide →Office chairsShould You Choose a Mesh or Leather Office Chair?Choose by fit first and material second. Mesh lets air through and flexes under you; leather and leather-look covers sit over foam padding that air…Read the guide →Office chairsWhich Office Chair Features Matter Most for Long Workdays?For eight-hour days, the chair has to support more than one position. OSHA's workstation guidance says that "working in the same posture or sitting…Read the guide →Office chairsIs a Weight Rating Enough When Choosing a Big-and-Tall Office Chair?No. A weight rating is the manufacturer's upper limit for the load, and you should stay under it, but it says nothing about whether the seat is wide…Read the guide →Office chairsWhat Should You Check in a Cross-Legged Office Chair?A cross-legged chair is a wide, often armless seat built so you can fold your legs under you. Check that it still works when you sit normally: the…Read the guide →Office chairsDo You Need a Built-In Footrest on an Office Chair?For desk work, the footrest you may need is a separate one on the floor. It solves a specific problem: the chair has been raised to suit the desk and…Read the guide →Office chairsHow Do You Choose an Office Chair Mat for Carpet or Hard Floors?Choose a chair mat rated for your floor surface and, for carpet, its pile depth. Many plastic carpet mats use grippers, while hard-floor versions use…Read the guide →Office chairsWhat Office Chair Works Best in a Small Space?In a small room the chair that works is the one that fits under the desk and rolls back far enough for you to stand, not the one with the smallest…Read the guide →Office chairsWhat Does an Ergonomic Office Chair Cost, and What Do You Get at Each Price?The chairs compared here ranged from $159.99 to $609.99 at the makers' US stores, checked 2026-10-13. A larger budget does not automatically buy a…Read the guide →Office chairsIs an Office Chair's Sale Price a Real Discount?A crossed-out price does not, by itself, establish a real saving. For a seller's former-price comparison, the FTC looks at whether the higher price…Read the guide →Office chairsWhich Armrest Adjustments Matter on an Office Chair (2D, 3D, 4D, Flip-Up), and Can You Upgrade Them?Start with height and width: OSHA asks for armrests low enough for "relaxed shoulders" and close enough to support the lower arms. Forward-back travel…Read the guide →Office chairsDo Seat Cushions and Lumbar Pillows Fix an Office Chair, or Make It Worse?A cushion can change how a chair fits, but it does not repair its adjustments. It raises your sitting position by the thickness left under your…Read the guide →Office chairsUnder-Desk Footrest or a Chair With a Built-In Footrest: What Each Costs and When You Need OneFor seated desk work, use a separate footrest if your feet cannot reach the floor after you set the chair for the work surface. CCOHS asks for support…Read the guide →Office chairsWhat Should You Check Before Buying a Used or Refurbished Office Chair?A used or refurbished chair is worth considering only after you identify the exact version, check its condition and read the guarantee that applies to…Read the guide →Office chairsWhat Do BIFMA, ANSI and CAL 117 Labels on an Office Chair Mean?ANSI/BIFMA X5.1 is a test standard for general-purpose office chairs; a listing that says only BIFMA does not identify which standard was used or…Read the guide →Office chairsWhat Do PU, Bonded and Genuine Leather Mean on a Chair Listing, and What Is a Double-Rub Count?Genuine leather refers to hide, while bonded material contains leather fibers mixed with other substances. PU identifies polyurethane, but the label…Read the guide →Office chairsIs a Gaming Chair Worse Than an Office Chair for Desk Work?Not because of the label; for desk work, compare the chair's adjustments. OSHA's chair guidance asks for an adjustable seat depth, height-adjustable…Read the guide →Office chairsKneeling Chairs and Saddle Stools: Who Are They For, and What Are the Trade-Offs?Kneeling chairs and saddle seats offer different ways to sit and change position, but the category name does not establish fit. A kneeling design uses…Read the guide →Office chairsHow Do You Fix an Office Chair That Sinks or Rolls Badly (Gas Cylinder and Casters)?For a chair that sinks, first ask the maker to check the height-control mechanism and identify a compatible replacement cylinder if needed. Replace…Read the guide →Office chairsDo You Need a Headrest on an Office Chair?A headrest is worth checking if you regularly recline and want support in that position. OSHA's purchasing guide calls for one when a backrest…Read the guide →Office chairsWhat Does an Office Chair Warranty Actually Cover?A chair warranty covers the failures, parts and purchasers specified in its terms, rather than everything that happens during the headline number of…Read the guide →Office chairsWhat Should a Short Person Check in an Office Chair?Check the lowest occupied seat height and the shortest usable seat depth first. You need foot support and enough space between the seat edge and your…Read the guide →

All office chairs guides · All guides and search