Desworthy Editorial Team
Desworthy editorial reviewer focused on ergonomic chair research, desk tech, affiliate disclosure, and practical UK home office buying decisions.
Last reviewed on by Desworthy Editorial Team.
Source information was checked on 7 October 2026. The editorial update date above does not mean prices, availability or retailer terms were checked again. Confirm those details with the retailer before buying.
If MARKUS already fits your legs and supports your back comfortably, a C300 replacement needs a specific reason. The three changes worth checking are seat geometry, lumbar movement and armrest positioning. More controls alone do not establish that the new chair will feel better.
The current C300 Black Standard listing was £249.99. For someone who already owns MARKUS, that is a replacement purchase, not merely the £90.99 gap between two new-chair listings. Current MARKUS Vissle Light Grey was £159.
Last verified: 7 October 2026. MARKUS measurements below refer to UK article 505.218.61; older versions should be measured directly rather than assumed identical.
1. Check what changes under your thighs
| Published UK dimension | Current MARKUS 505.218.61 | Standard C300 | Consequence to check |
|---|---|---|---|
| Seat depth | 47 cm | 43.5–46 cm listed | Compare the actual usable front edge at your supported sitting position |
| Minimum seat height | 46 cm | 47 cm | C300’s published minimum is 1 cm higher, not lower |
| Maximum seat height | 57 cm | 55 cm | Do not assume the more adjustable-looking chair reaches a higher position |
| Seat width | 53 cm | 49.5 cm | The current MARKUS seat is 3.5 cm wider on paper; arm spacing is a separate measurement |
Sources: current IKEA UK MARKUS and standard C300 UK.
The C300 page describes depth adjustment in its FAQ, while comparison material has given different information about the base chair. Confirm the exact selected UK control if a slide is essential. The listed numbers alone cannot establish how the seat will feel against your legs.
Photograph or record the position in which your current MARKUS works best. Keep the same desk height during a comparison. Otherwise, a changed setup can be mistaken for an improvement caused by the chair itself.
2. Check the moving lumbar contact
MARKUS lists lumbar support without separate height/depth controls. C300 describes a self-adaptive dynamic section. If you dislike the fixed contact position in your current chair, that different layout gives you a reason to try C300.
Pay attention to where the support touches as you move, rather than trying to tolerate a pad that feels uncomfortable because it is advertised as ergonomic. A moving section can feel more useful to one person and more intrusive to another. The sources do not supply a measured pressure comparison between these exact chairs.
For a manually positioned alternative, read M57 versus MARKUS or C300 versus M57. That separates a need for lumbar adjustment from a preference for adaptive movement.
3. Check the arms at your desk
C300 lists coordinated 4D armrests; current MARKUS does not list an equivalent set of separate pad controls. If your old arms stop the chair moving close enough to the desk, extra adjustment may be useful.
Test typing, mouse use and a supported recline. The pad should be useful where your forearm naturally rests, and the chair should fit beneath or beside the desk as intended. Do not judge this only from an armrest-direction count or a showroom recline.
The HSE workstation checklist helps assess supported feet, thigh clearance, back support and working reach together. Keep a short record of those points during your trial so the decision is based on repeatable observations.
Questions before replacing MARKUS
Is C300 a narrower seat than the current MARKUS?
The cited seat widths are 49.5 cm and 53 cm, a 3.5 cm difference. That does not describe usable clearance between the armrests or the dimensions of an older MARKUS version.
Is C300 better for shorter legs?
Its listed depth range is shorter than the current MARKUS’s 47 cm depth, but its minimum seat height is 1 cm higher. Check both constraints and confirm the actual depth control on the selected version.
Should I replace a MARKUS that is comfortable?
Only for a specific benefit you want, such as different lumbar movement or useful arm positioning. Replacing it merely to add adjustment directions can create a new fit problem without resolving an existing one.
Is the upgrade cost £90.99?
That is the difference between two current new-chair listings: £249.99 minus £159. If you already own MARKUS, your C300 purchase is £249.99 before delivery, codes and any separately established resale proceeds.
What should I check before a home trial?
Get the applicable return conditions and transport cost before assembly. Read Sihoo’s main policy and after-sales policy; a dislike of fit is not automatically a defect claim with free return transport.
Reference and calculation notes
Sources were checked on 7 October 2026. Product geometry and controls are attributed to the exact UK source versions. The 1 cm height, 3.5 cm width and £90.99 differences are Desworthy calculations, not measurements from a physical comparison. Keep the current C300 offer and Sihoo model guide alongside the fit check.
Image credit: Sihoo, product photograph.
Note: This article is for reference only.