Independent comparisons. We may earn from shop links. More info

115mm vs 125mm angle grinder

Updated: October 2026

You have used a small grinder on brackets and studs, and a five-inch disc looks like the same tool with a little more reach. The useful question in a 115mm vs 125mm angle grinder choice is not which number sounds more professional. It is whether you need the extra depth a 125 mm wheel can publish, and whether you are about to get that depth by putting a larger disc on a guard that was never meant for it. This page can send you back to 115 mm, or on to a 230 mm hire. The [125 mm angle grinder comparison](/hub/tools/angle-grinder-125mm) assumes you already want the larger of these two small classes. Updated October 2026 from retailer and HSE sources, not from a lab. Amazon links may earn a commission at no extra cost to you.

You have used a small grinder on brackets and studs, and a five-inch disc looks like the same tool with a little more reach.

Our top picks

Bosch Bosch GWS 7-125

Best overall

Bosch Bosch GWS 7-125
8.2/10about £71.98
View offer
TOPWAY TOPWAY 750 W

Alternative

TOPWAY TOPWAY 750 W
6.7/10about £23.99
View offer
DEWINNER DEWINNER 1,000 W

Best value

DEWINNER DEWINNER 1,000 W
7.0/10about £48.99
View offer
On this page
  1. 1.Same spindle, different guard
  2. 2.What the extra diameter buys
  3. 3.When 115 mm is the better buy
  4. 4.Titles that say both

Same spindle, different guard

Most 115 mm and 125 mm grinders in the UK share an M14 spindle and a 22.23 mm disc bore. Top 7 Tools sets that out clearly, and it is why the discs feel interchangeable when you hold them. The nut will often start on the wrong machine. That fit is the trap. The machines are not the same tool with a different sticker, because the guard, the flanges and the stated wheel diameter belong together. HSG17 treats the guard as more than a spark deflector. It contains fragments, it reduces the chance of contact, and it is there so an oversize wheel is not fitted. The serious accidents in that history include wheels run with the guard removed so a larger disc would go on. We will not describe how to take a guard off. If your 115 mm grinder will not accept a 125 mm disc with the guard in place, the answer is a 125 mm grinder, not a modification. The safer direction is using up old 115 mm discs on a new 125 mm body. UK Tool Guide notes that the bore often matches and that a smaller disc can be allowed when the manufacturer says so. Often is not permission. Read the manual for the grinder in your hand. A smaller disc on a larger guard can be acceptable. A larger disc on a smaller guard is the pattern HSG17 is warning you about. Fitting steps, once the disc and the guard already match, are on the how to use page.

What the extra diameter buys

It does not automatically buy more watts. Top 7 Tools compares Makita's 115 mm GA4530R and 125 mm GA5030R at the same 720 W and the same 11,000 rpm. The published maximum cutting depths on that pair are about 30 mm for the 115 mm model and about 35 mm for the 125 mm model. Five millimetres is the whole more-reach story on those two sheets. Those Makita models are not ASINs in our comparison. They are the cleanest published pair we can cite so you do not invent a universal depth for every body on amazon.co.uk. ManoMano's UK guide cites depths that do not match that Makita pair exactly, so there is no single class depth. The GWS 7-125 listing does not print one. Do not borrow 35 mm from a different brand. An extraction guard spends some of that depth. Bosch Professional's UK dust page for concrete cutting describes 125 mm extraction shrouds with about 25 mm of maximum cut once the shroud is on. If you need the dust control, you do not also get the full open-cut figure. A slab thicker than the real depth is not solved inside this size class. That limit is the paving guide.
Bosch Bosch GWS 7-125

Testsieger

Bosch Bosch GWS 7-125
8.2/10about £71.98
View offer

When 115 mm is the better buy

Toolstation's buying guide puts 115 mm with precision and light work, and 125 mm as the versatile middle that is still not a heavy cutter. A 115 mm body is often slightly easier in a joist bay, on a trailer coupling, or on a cut where the guard of a 125 mm tool fouls the adjacent steel. For bolts, thin sheet and small welds, the extra 10 mm of disc rarely changes the job, and the smaller guard can be the one that actually fits. Choose 125 mm when the cut is deep enough that 30 mm is not enough and about 35 mm might be, on a tool that publishes a depth, or when you are already buying discs in the five-inch size and you want one guard that matches them. Do not choose it because a listing printed 1,200 W. Power and diameter are separate lines. Wattage, plugs and switches are ordered on the buying guide linked below. This page only decides the class. For paving, 125 mm is the better of these two only while the slab is inside the depth you can cut. A thicker slab is a 230 mm hire, not a 115 mm tool asked to do more.

Titles that say both

Two tools in this set print both sizes in the amazon.co.uk title and then claim 125 mm in the bullets. The TOPWAY 750 W, ASIN B08HXQVSFN, is £23.99, 750 W, 11,000 rpm, 4.2 from 193 reviews, and the title says 115 mm and 125 mm. The TOPWAY 1,200 W budget model, ASIN B0G3KN6V8W, is £29.99 with the same double title, a speed dial, and 3.3 from five reviews. A bullet that says 125 mm blade capacity does not settle the guard. You need the guard in the photograph, or in your hands, to match one class. A title that hedges is how people order a 115 mm body and turn up with a pack of 125 mm discs.

Common questions

Is 125 mm just a more powerful 115 mm?
No. On the Makita pair Top 7 Tools cites, the 115 mm GA4530R and the 125 mm GA5030R are both 720 W and 11,000 rpm. The difference they publish is cutting depth, about 30 mm against about 35 mm. Watts are a separate specification. A cheap 1,200 W sticker does not make a 125 mm grinder the powerful version of a 115 mm one.
How much deeper does 125 mm cut?
Use a figure for a named model. The Makita pair above is about 5 mm deeper at 125 mm. ManoMano's guide cites depths that do not match those numbers exactly, so there is no single depth for the class. An extraction shroud can cut the usable depth further, to around 25 mm on Bosch's 125 mm concrete-cutting guard. If your tool prints no depth, do not borrow 35 mm from a different brand.
Can I put a 125 mm disc on my 115 mm grinder?
Not by taking the guard off. The bore may match, and that is why the disc will seem to fit. HSG17 treats an oversize wheel with the guard removed as a known serious accident pattern. If the guard will not close over the disc, the disc is wrong for that grinder. Buy a 125 mm machine instead.
Can I use up my old 115 mm discs on a new 125 mm grinder?
Only if that grinder's manufacturer allows a smaller disc. The bore is often 22.23 mm on both, which is why they bolt up. Permission still has to come from the manual for your model, not from the fact that the nut turned. The dangerous swap is the other way: a 125 mm disc on a 115 mm guard.
Do they use the same spindle?
In this class, usually yes: M14, with a 22.23 mm bore. That is the normal UK small-grinder pattern Top 7 Tools describes. It is not universal in our set. The Makita XAG25Z uses X-LOCK and will not take an ordinary threaded disc. Check the spindle before you buy a pack of wheels.
Which size for bolts and sheet metal?
A 115 mm grinder is the better fit when access is tight and the material is thin. Toolstation puts that size with light, precise work. A 125 mm tool will also cut sheet, but the larger guard can foul the work. You do not need the extra diameter for a bolt you can already reach.
Why do some Amazon titles say 115 mm and 125 mm?
Because the listing is hedging. In this set the TOPWAY 750 W and the TOPWAY 1,200 W both print the two sizes in the title while the bullets claim 125 mm. Open the guard details before you buy discs. One title cannot be a safe specification for two guards.

Related pages

125 mm angle grinder buying guide

125 mm angle grinder

Best 125mm angle grinder: the Bosch or DEWINNER

Cut paving slabs with a 125mm grinder at home

How to use a 125mm angle grinder at home safely

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are the amazon.co.uk figures stored for these eleven listings. HSE duties and PUWER apply at work. They are not a certificate for a domestic grinder. A shared review block is one sample. US review text is not UK opinion.

  1. HSE, PUWER FAQ (retrieved October 2026)
  2. HSE, HSG17 (retrieved October 2026)
  3. OPSS, PSA5 toothed saw blades (retrieved October 2026)
  4. FEPA, EN 12413 safety leaflet (retrieved October 2026)
  5. BSI, BS EN IEC 62841-2-3 (retrieved October 2026)
  6. Bosch Professional, GWS 7-125 (retrieved October 2026)
  7. Electrical Safety First, angle grinders (retrieved October 2026)
  8. Screwfix, angle grinder buying guide (retrieved October 2026)
  9. Top 7 Tools, disc size and depth (retrieved October 2026)