What size base each model needs, what changed from 8th Edition, and whether you actually have to rebase the army in your loft.
Start here: three rules that govern everything
Most base size guides hand you a chart and leave. The chart is the easy part — and on its own it will get you the wrong bases. Three rules decide what you actually need.
- Square and rectangular bases only. The Old World is a rank-and-flank game. Every model is mounted on a square or rectangular base — there are no round bases anywhere in the system. If you are coming from Age of Sigmar or 40,000, everything gets rebased.
- Base size is set per unit, not per troop type. This is the one that catches people out. There is no rule that says "all monstrous infantry use 40x40mm". Each unit entry in each army book names its own base size. Chaos Ogres are 40x40mm; Skin Wolves are 50x50mm. Both are monstrous infantry.
- Some entries give a range, not a size. A few entries list a minimum and a maximum — the Bretonnian Warhorse is 25x50mm minimum, 30x60mm maximum. Where a range is given, the base the model was supplied with is the correct one to use.
Do you actually have to rebase?
For a game at home with a friend, no. For a tournament, yes. The rulebook draws that line explicitly:
Whilst it is possible to play a game of Warhammer: the Old World without needing to re-base such models, in Matched Play events players are required to use correctly based models to ensure all aspects of the game are as fair as possible.
— Warhammer: The Old World rulebook, page 98
Worth knowing that this is firmer than what Games Workshop said before launch. The April 2023 development diary suggested organised play would probably require appropriate basing, and floated movement trays as a workaround. The published rulebook says players are required to use correctly based models, and makes no mention of trays as a substitute.
So: if you play casually, your 8th Edition army is fine as it stands. If you intend to take it to an event, budget for rebasing — and read on, because it is probably a smaller job than you fear.
What changed from 8th Edition
Games Workshop's own summary, from the April 2023 development diary, was short:
All 20mm bases have been replaced with 25mm bases. Most (but not all) 25mm and 25x50 bases have been replaced with new-sized bases.
— Games Workshop, Old World development diary, 14 April 2023
That is the whole of the official before-and-after. GW has never published a comparison chart, which is why the guides you will find online disagree with each other. Here is what the unit entries themselves show.
Infantry: 20mm is gone
The 20x20mm base is no longer used. Rank-and-file infantry that sat on 20mm now sits on 25x25mm — Night Goblins being the obvious example. If a guide tells you 20mm is still a current Old World size, it is out of date.
A 30x30mm infantry base was also introduced, which was not a standard rank-and-file size in 8th. Chaos Warriors use it.
Cavalry: it depends on the mount, not the rider
You will read almost everywhere that heavy cavalry and knights moved up to 30x60mm while light cavalry stayed on 25x50mm. That is not the rule, and it will cost you money if you buy on it.
Pistoliers and Marauder Horsemen are light cavalry by any definition, and both are on 30x60mm. Goblin Wolf Riders are on 25x50mm. The dividing line is not how heavily armoured the rider is — it is what the model is sitting on.
The rule that actually works: horses go on 30x60mm — knights, pistoliers, outriders, marauder horsemen. Smaller mounts stay on 25x50mm — wolves, warhounds and similar keep the old cavalry footprint. Check the unit entry before a large order either way, but this will predict it correctly far more often than the heavy-versus-light split will.
Bretonnia is a special case — and it is good news
If you play Bretonnia, you may not need to rebase your knights at all. Games Workshop's Forces of Fantasy errata sets the Bretonnian Warhorse as 25x50mm minimum, 30x60mm maximum. Both sizes are legal.
No other base size guide we are aware of mentions this, and it is the single largest rebasing job it could save you.
The size reference
Every size below is confirmed against a published unit entry or Games Workshop errata. The examples are illustrative, not exhaustive — and per rule 2, always check your own unit entry.
| Size | What uses it | Confirmed examples | Bases |
|---|---|---|---|
| 25 x 25 mm | Rank-and-file infantry, war machine crew | Night Goblins, war machine crews | 25mm square |
| 30 x 30 mm | Bulkier and elite infantry, some foot characters | Chaos Warriors, Marauder Chieftain | 30mm square |
| 40 x 40 mm | Monstrous infantry, swarms | Chaos Ogres, Rat Swarms | 40mm square |
| 50 x 50 mm | Larger monstrous infantry | Skin Wolves | 50mm square |
| 25 x 50 mm | Smaller mounts — wolves and hounds | Goblin Wolf Riders | 25 x 50mm |
| 30 x 60 mm | Horse-mounted cavalry, heavy and light alike | Empire and Chaos Knights, Pistoliers, Marauder Horsemen | 30 x 60mm |
| 40 x 60 mm | Flying mounts | Pegasus Knights | 60 x 40mm |
| 50 x 75 mm | Monstrous cavalry, most war machines, larger single monsters | Demigryph Knights, Dragon Ogres, Great Cannon | 50 x 75mm |
| 50 x 100 mm | Chariots | Orc Boar Chariot | 50 x 100mm |
| 60 x 100 mm | Very large war engines | Screaming Bell | 60 x 100mm |
| 100 x 150 mm | The largest monsters and engines | Chaos Dragon, Hellcannon | 100 x 150mm |
War machines carry two sizes. The engine and its crew are based separately — a Great Cannon is 50x75mm for the gun and 25x25mm for the crew, and a Hellcannon is 100x150mm with its handlers on 25x25mm. Order for both.
How to check your own units
Because sizes are set per unit entry, the army book is the answer for anything not listed above. Two things worth knowing before you trust a printed entry:
- Games Workshop still corrects base sizes after release. Several units have had their size changed by errata since launch, so the printed page in your army book is not always current.
- The FAQ and errata documents are free. Check the current versions on Warhammer Community before a large order — they list corrections unit by unit with army book page references.
If a unit entry gives a minimum and a maximum, the base your model came with is the correct one.
Basing an army from here
We make every size listed in this guide, in square and rectangular, 3D printed to order in the USA. All of them have a textured top for glue and flock to key into, and magnet holes printed straight in that hold a magnet by friction — no glue needed, which matters when you are doing two hundred of them.
- Square Bases — 15mm to 150mm, including every Old World infantry size
- Rectangular Bases — 25x50mm to 100x150mm for cavalry, chariots and monsters
- Square Movement Trays — move a regiment in one piece once it is ranked up
Sources and corrections
Last verified against Games Workshop FAQ & Errata v1.5.3 (July 2026).
Everything in this guide is drawn from Games Workshop's own published material, checked against unit entries rather than paraphrased from other guides:
- Warhammer: The Old World rulebook, page 98 — base shape, Matched Play requirement, and the min/max rule.
- Old World development diary, Warhammer Community, 14 April 2023 — the 20mm to 25mm change and Games Workshop's rationale.
- FAQ & Errata for the rulebook, Forces of Fantasy and Ravening Hordes — per-unit corrections including the Bretonnian Warhorse range.
- Published unit entries across the current army books and Arcane Journals.
Games Workshop releases new Arcane Journals regularly, and new unit entries arrive with their own base sizes. If you spot something here that no longer matches a current entry, tell us and we will correct it — this page is maintained, not published once and forgotten.
Terrain Genesis is an independent manufacturer. Warhammer, The Old World, and all associated names are trademarks of Games Workshop Limited. Terrain Genesis products are not affiliated with, licensed by, or endorsed by Games Workshop. This guide is provided as a compatibility reference for hobbyists and is not a substitute for the published rules.