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230 mm vs 115 mm angle grinder: which size fits your job?

Updated: 22 October 2026

You already own a 115 mm grinder, or you are staring at a Bosch code that contains a nine, and you need to know whether a 9 inch or 230 mm machine is worth the weight and the kick. The decision is not more watts alone. Disc diameter changes cut depth, rpm, guard size and how violently the tool reacts when the blade binds. This page compares sizes using UK guide figures and the kept models on our [9 inch angle grinder comparison](/hub/tools/9-inch-angle-grinder). Peter F. read those figures against the listings on 19 October 2026. There was no laboratory test. A qualifying purchase can earn a commission at no extra cost to you.

You already own a 115 mm grinder, or you are staring at a Bosch code that contains a nine, and you need to know whether a 9 inch or 230 mm machine is worth the weight and the kick. The decision is not more watts alone.

Our top picks

Evolution Evolution R230DCT

Best overall

Evolution Evolution R230DCT
9.4/10about £119.95
View offer
JCB JCB 21-AGTPK twin pack

Alternative

JCB JCB 21-AGTPK twin pack
8.2/10about £90.50
View offer
Einhell Einhell TE-AG 230/2000

Best value

Einhell Einhell TE-AG 230/2000
8.0/10about £68.99
View offer
On this page
  1. 1.Same name, different disc
  2. 2.Depth and speed
  3. 3.When the small grinder is the better tool
  4. 4.A straight recommendation

Same name, different disc

Shoppers say 9 inch, 230 mm and large angle grinder interchangeably for the same wheel class. 125 mm sits between 115 mm and 230 mm on some counters but behaves like a small grinder in depth terms, not like a 9 inch tool. The trap is model names. Bosch GWS 9-115 is a 115 mm grinder where 9 is a power class, not nine inches. Always read the disc diameter line on amazon.co.uk, not the marketing number in the middle of the model string. This comparison also includes a JCB twin pack with both 115 mm and 230 mm tools. That listing answers I want both sizes, not which single size should I buy. The Evolution R230DCT is a 230 mm disc cutter on wheels, not a replacement for a 115 mm grinder on light metal.

Depth and speed

Retailer and manufacturer guides quote approximate cutting depths, not guarantees for your slab. Screwfix's angle grinder buying guide uses about 30 mm for 115 mm and about 70 mm for 230 mm. Top7tools.uk cites Makita published depths near 30 mm for 115 mm, 35 mm for 125 mm and 68 mm for a 230 mm GA9020 as examples. The Evolution cutter in this set states 90 mm depth in its title. That is its own listing claim for a wheeled cutter, not the Screwfix handheld figure. Speed marking matters as much as depth. A 230 mm disc is rated for far lower rpm than a 115 mm disc. EN 12413 tables put 230 mm near 6,650 rpm at 80 m/s versus 115 mm near 13,300 rpm. Fitting a large disc on a small grinder by removing the guard is unsafe, and at work it conflicts with the guarding rules those tables sit inside. The rpm mismatch can burst the wheel. iSafe's toolbox talk prefers the smaller grinder when it can do the job. That is sound advice when your cut is only a few millimetres deep.
Evolution Evolution R230DCT

Testsieger

Evolution Evolution R230DCT
9.4/10about £119.95
View offer

When the small grinder is the better tool

Choose 115 mm or 125 mm when guide depths around 30–35 mm clear the material, when you work overhead or in a cupboard, or when you mainly dress welds and cut thin stock. UK round-ups often tell most buyers to buy 115 mm first and treat 230 mm as a second, more demanding tool for thick steel or paving. Weight backs that advice. In this set, handheld 230 mm bodies run from about 4.94 kg on the Hilka to 6.4 kg on the 2,350 W Einhell, before you add a heavy diamond blade. A 115 mm unit is easier to control on a ladder or bench. Noise and vibration still matter on large tools. HSE bulletins cite grinder noise around 90–95 dB(A) and vibration limits that bite within tens of minutes of continuous use at work. At home, fatigue arrives sooner on a 230 mm span.

A straight recommendation

Buy or hire 230 mm when you must cut slabs, blocks, kerbs or thick sections deeper than about 30–40 mm in one sensible pass, and you can hold the tool with two hands, guard on, and a dust plan for masonry. Stay with 115 mm for tiles, bolts, most sheet metal and tidy-up grinding unless you already know the small disc bottoms out. If you only have one or two thick cuts, hiring a 230 mm cutter or booking a landscaper can beat buying a corded body in the about £68 to £156 band plus discs and PPE. When you buy, the Einhell TE-AG 230/2000 is the usual best value handheld in this file. The Evolution R230DCT is the top pick when paving drives the purchase. Model matching sits on best 9 inch angle grinder, not on this size page.

Common questions

How much deeper does 230 mm cut?
Guide figures cluster near 30 mm for 115 mm versus 65–70 mm for a 230 mm handheld on retailer tables. The Evolution cutter claims 90 mm as its own spec.
Is a 9 inch grinder just a stronger 115 mm?
No. It is a different disc class, speed rating, guard and risk profile, not only wattage.
Can I put a 230 mm disc on a small grinder if I remove the guard?
No. The rpm marking will not match, and the guard is required.
What does GWS 9-115 mean?
A 115 mm Bosch grinder. The nine is not inches.
Is 125 mm a third class or almost a 115 mm?
It is a real mid size with depth between the two, but many buyers still choose 115 mm or jump to 230 mm for slabs.
When is hire smarter than buying 230 mm?
For a handful of thick cuts where hire includes a legal disc and you avoid storing a heavy tool.
Will a 115 mm finish a 40 mm slab in one pass?
Usually not if guide depths near 30 mm apply. You face multiple passes, chisel work, or stepping up to 230 mm.
Does corded or cordless change the size choice?
In this amazon.co.uk set every kept 230 mm row is corded at 2,000 W or more. Cordless 230 mm kits appear on trade counters but are not in this comparison. A 115 mm cordless grinder you already own still cannot safely mount a 230 mm disc.

Related pages

230 mm angle grinder buying guide

How to use a 9 inch angle grinder

Angle grinder for paving slabs

9 inch angle grinder

Best 9 inch angle grinder picks for UK jobs in 2026

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the seven amazon.co.uk listings captured on 19 October 2026. PUWER, HSG17 and the silica limit apply at work. They are not a certificate for a domestic grinder. A dust port is not extraction on its own.

  1. HSE, PUWER overview (retrieved 19 October 2026)
  2. HSE, HSG17 Safety in the use of abrasive wheels (retrieved 19 October 2026)
  3. HSE, Chasing concrete and raking mortar (retrieved 19 October 2026)
  4. HSE, INDG463 Control of exposure to silica dust (retrieved 19 October 2026)
  5. HSE, Angle grinder bulletin (retrieved 19 October 2026)
  6. FEPA, Safety leaflet for bonded abrasives (retrieved 19 October 2026)
  7. Screwfix, Angle grinder buying guide (retrieved 19 October 2026)
  8. Electrical Safety First, Angle grinders (retrieved 19 October 2026)