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115mm or 125mm angle grinder

Updated: October 2026

You are choosing between the Ryobi 115 mm body and the 125 mm DeWalt, DCA and Dong Cheng tools, and the discs look as if they should swap. A 125 mm wheel does not belong on a 115 mm guard. If you are buying one full-size cordless grinder and you have no stock of 115 mm discs, 125 mm is the more useful size in this set. If you already own Ryobi ONE+ packs and 115 mm discs, the R18AG-0 matches that stock. This page answers 115mm or 125mm angle grinder. Kit or bare tool is the [buying guide](/hub/sanders/cordless-angle-grinder/sub/cordless-angle-grinder-buying-guide). Every row is on the [cordless angle grinder comparison](/hub/sanders/cordless-angle-grinder). How the disc then cuts steel is the [cutting metal page](/hub/sanders/cordless-angle-grinder/sub/cordless-angle-grinder-cutting-metal).

You are choosing between the Ryobi 115 mm body and the 125 mm DeWalt, DCA and Dong Cheng tools, and the discs look as if they should swap. A 125 mm wheel does not belong on a 115 mm guard.

Our top picks

Ryobi Ryobi R18AG-0 115 mm bare

Best overall

Ryobi Ryobi R18AG-0 115 mm bare
9.4/10about £66.65
View offer
DeWalt DeWalt DCG407N-XJ 125 mm bare

Rank 2

DeWalt DeWalt DCG407N-XJ 125 mm bare
9.4/10about £107.50
View offer
DCA DCA ADSM06-125 125 mm kit

Best value

DCA DCA ADSM06-125 125 mm kit
8.6/10about £56.98
View offer
On this page
  1. 1.What the two sizes change
  2. 2.Same bore, different guard
  3. 3.Which of these grinders is which
  4. 4.76 mm is not the same decision

What the two sizes change

Both sizes are handheld grinders. Hilti's UK buying guide treats 115 mm and 125 mm as the common sizes, and 230 mm as a different tool for structural section. The useful difference on a bracket or a bolt is depth, and two UK sources measure it differently. Abrasive Finishing Systems give useful cutting depth of about 16.5 mm on a 115 mm disc and about 21.5 mm on a 125 mm disc, on otherwise similar bodies. Top 7 Tools report Makita corded depths of about 30 mm on 115 mm and about 35 mm on 125 mm, and they cite HSG17 against taking a guard off for an oversize wheel. Do not fold 16.5 mm and 30 mm into one number. They are not the same measurement. Both pairs show about 5 mm more depth on the larger disc. Buy the diameter you mean to use, with the guard sold for it.

Same bore, different guard

Full-size UK trade discs use a 22.23 mm bore. The DCA listing states 22 mm, or 7/8 inch, for its 125 mm wheel. That is the same nominal bore family. The guard stops the sizes being interchangeable. A 115 mm guard is made for a 115 mm disc. A 125 mm disc sits inside it only if you open the guard, and HSG17 treats that oversize-wheel habit as an accident theme. The bore is shared. The guard is the difference. Buy the diameter printed for that guard, and check the bore. A disc with the right diameter and the wrong bore is still the wrong disc.
Ryobi Ryobi R18AG-0 115 mm bare

Testsieger

Ryobi Ryobi R18AG-0 115 mm bare
9.4/10about £66.65
View offer

Which of these grinders is which

In this amazon.co.uk set, the Ryobi and the SoarFly are 115 mm. The DeWalt, the DCA, both Dong Cheng models and the NANWEI are 125 mm. The Seesii is titled 4-1/2 inch. That inch name is often used for the smaller full-size class, and the title is not a measured 115.0 mm of cutting depth. Read the millimetre line on the body, not a nickname in the headline.

76 mm is not the same decision

A 75 mm or 76 mm mini is not a third full size that spins faster. The TEENO uses a 10 mm bore. That bore does not take a 22.23 mm trade disc, and a full-size wheel does not belong on the mini's guard. Use this page when the choice is 115 mm or 125 mm, both full-size, with a 7/8 inch nominal bore. This page is from the Products Compared editorial team, updated on 15 October 2026. Depth figures are from Abrasive Finishing Systems and from Top 7 Tools on Makita corded tools, not from a lab cut of ours. A qualifying purchase through our links can earn a commission at no extra cost to you.

Common questions

Is 115 mm enough for brackets and bolts?
Often, yes, for a thin bracket or a bolt you can approach square on. Abrasive Finishing Systems put useful cutting depth at about 16.5 mm on a 115 mm disc, against about 21.5 mm on 125 mm. If that extra depth is the difference between one pass and a second, 125 mm is the easier body. If you already own 115 mm discs and Ryobi ONE+ packs, the R18AG-0 matches the stock you have.
Can I fit a 125 mm disc on the Ryobi?
No. The Ryobi in this set is a 115 mm body, and the guard is part of that size. HSG17 treats removing a guard for an oversize wheel as an accident pattern. The bore may match a 125 mm trade disc. The guard will not. Buy 115 mm discs for that tool, or buy a 125 mm body if that is the disc you want to keep.
Is 4-1/2 inch the same as 115 mm?
It is the usual inch name for the smaller full-size class, and it is not a measured cutting depth. The Seesii in this set is titled 4-1/2 inch and does not state a 115.0 mm depth. The Ryobi and the SoarFly are the bodies here that are stated as 115 mm. Match the disc to the millimetre size on the tool, not to an inch phrase in a title.
Do both sizes use the same bore?
The full-size pair does, in nominal terms. UK trade discs are 22.23 mm. The DCA listing states 22 mm, or 7/8 inch, for its 125 mm disc. A 115 mm body such as the Ryobi takes that same nominal bore and still takes a 115 mm disc only. The TEENO mini is a 10 mm bore. Do not buy mini discs for a 125 mm spindle, or 22.23 mm discs for a 10 mm mini.
Does a higher rpm on the mini beat a 125 mm tool?
No. Cutting depth follows the disc diameter and the guard, not a spindle speed printed to make a small tool sound larger. The mini cannot take the 125 mm wheel, and the TEENO's 10 mm bore is a different fitting from 22.23 mm. Use the mini for the light job its listing allows. Use a 125 mm body when the cut needs the depth described above.

Related pages

Sanders

Cordless angle grinder

Best cordless angle grinder UK for XR packs or a kit

Cordless angle grinder buying guide for kit or body

Cutting metal with a cordless angle grinder safely

How to use a cordless angle grinder: disc and guard

Sources

Public UK sources named for workplace guards, abrasive wheels, vibration, and the grinder standard. amazon.co.uk prices, stars, and review counts are the figures stored for these twelve listings. Prices move.

  1. HSE, PUWER overview (retrieved October 2026)
  2. HSE, HSG17, Safety in the use of abrasive wheels (retrieved October 2026)
  3. HSE, INDG175, hand-arm vibration (retrieved October 2026)
  4. Control of Vibration at Work Regulations 2005, regulation 4 (retrieved October 2026)
  5. IEC 62841-2-3:2020, particular requirements for hand-held grinders (retrieved October 2026)
  6. OSA, EN 12413 marking note for bonded abrasives (retrieved October 2026)
  7. Electrical Safety First, angle grinders (retrieved October 2026)