Base size is one of those topics where the practical answer is simpler than the internet suggests. For almost every model, the correct base is the one that came in the box. The complications arise with second-hand models, conversions, older miniatures and third-party bases, where the original base is missing or was never the current size.
This guide explains how base sizing works, how to measure accurately, and what to check before committing to a rebasing project.
An important note on accuracy
Unlike some other Games Workshop systems, Warhammer 40,000 has historically not had a single consolidated published base-size list covering every unit. In practice the base supplied with a kit is the reference point, and datasheet or FAQ material is where changes get communicated.
Because of that, this guide deliberately does not reproduce a unit-by-unit table from memory. Sizes shift between editions and box refreshes, and a chart copied from an old source is worse than no chart at all. Where a specific model matters to you, check the current official material or the base the current kit ships with, and check with your event organiser if you are playing competitively.
For context at the time of writing: Warhammer 40,000 11th Edition launched in June 2026, and no base-size changes were announced alongside it. Armies built to the previous edition's sizes were not invalidated. That remains the situation as far as we are aware, but it is exactly the sort of thing worth verifying independently before you rebase anything.
What base diameter means
Base diameter is the width of the base measured across its widest point, in millimetres, from outside edge to outside edge. A 32mm base is 32mm across the plastic, not 32mm across the recessed inner section and not 32mm including any decoration you have added.
Base sizes are described by that outer dimension because that is what determines the model's footprint on the table, which is what actually affects play.
Round and oval bases
Two shapes are in common use.
Round bases are used for the majority of infantry and many larger models. Commonly encountered diameters include 25mm, 28.5mm, 32mm, 40mm, 50mm, 60mm, 80mm, 90mm, 100mm, 130mm and 160mm. The 32mm round has been the standard for much modern infantry for around a decade, with 25mm remaining common on older and smaller models.
Oval bases are used where a model is long rather than round: bikes, cavalry, sprawling monsters and many vehicles. They are described by two dimensions, length by width. Commonly encountered sizes include 60x35mm, 75x42mm, 90x52mm, 105x70mm and 120x92mm.
Oval bases are usually placed with the long axis running front to back, following the model's facing, though this is a convention rather than something you should assume in every case.
How to measure a round base
- Turn the base upside down if the model allows, or measure across the top rim.
- Place digital calipers across the widest point, jaw to jaw, at the outer edge.
- Take two or three readings at different angles. Injection-moulded bases are not perfectly circular and can vary by a few tenths of a millimetre.
- Round to the nearest standard size. A reading of 31.8mm is a 32mm base.
How to measure an oval base
- Measure the longest axis first. This is the first number in the size description.
- Measure the widest point perpendicular to that axis. This is the second number.
- Take both measurements at the outer rim, not the inner recess.
- Match against known sizes; the gaps between standard oval sizes are wide enough that near-misses are usually measurement error rather than a non-standard base.
A cheap digital caliper is worth owning if you do any amount of rebasing or magnetising. Measuring by eye against a ruler is where most base-size confusion originates.
Why base size matters
Base size is not cosmetic. Several aspects of play depend on it:
- Footprint. A larger base occupies more table space, which affects how many models fit into a position and how easily a unit can be arranged.
- Positioning and measurement. Distances are measured to and from models, so base edges affect reach and spacing.
- Unit spacing and coherency. How a unit stays together is measured between models, so base size affects how far a unit can spread.
- Stability. A large, top-heavy model on an undersized base falls over constantly and is more likely to be damaged.
- Visual scale. Bases establish relative size. A model on a base that is obviously too small looks wrong even to people who do not play.
We have deliberately kept this general rather than quoting rules text; the current rulebook is where the specifics live.
Why different models use different footprints
Base sizes broadly scale with a model's physical bulk and the space it should reasonably occupy. Standard infantry sit on smaller rounds, heavier infantry step up, and monsters and vehicles use large rounds or ovals.
Sizes have also grown over time. Many models that shipped on 25mm bases in earlier decades are supplied on 32mm today, reflecting both larger sculpts and more elaborate posing. This is why second-hand models often arrive on bases that no longer match the current kit.
Do older miniatures need rebasing?
The honest answer is that it depends, and anyone giving you an absolute rule is oversimplifying.
For casual play, a conversation with your opponent settles it. Most players are entirely relaxed about older models on their original bases, and there is a reasonable argument that a coherent, consistently based older army is better than a mixed one.
For organised events, the event organiser's requirements are what matter, and they vary. Some enforce current sizes strictly, some allow models on their original supplied bases, and some publish their own policy. Check the specific event's pack rather than assuming.
Practical considerations worth weighing:
- Rebasing a painted army is time-consuming and carries real risk of damage.
- Partial rebasing looks inconsistent, so it is usually all or nothing within a unit.
- If you rebase, do it once and to current sizes rather than an intermediate guess.
- If you are unsure and not attending events, leave it. You can always rebase later; you cannot un-damage a model.
Base size and magnetising
Base diameter interacts with magnetising in two ways.
First, the recess under the base sets your magnet thickness limit, and larger bases generally have deeper and wider recesses to work with. Second, larger bases usually carry heavier models, so the holding force needs to scale accordingly, and two spaced magnets often outperform one central magnet on a big base.
Measure the recess rather than assuming it scales predictably with diameter, because it does not. Our step-by-step guide to magnetising miniature bases covers depth measurement, adhesive choice and testing.
Decorative base extensions
Sculpted rock, rubble, wreckage and similar additions are a normal part of basing, but there is a line worth being aware of.
Decoration that stays within the base rim changes nothing functionally. Decoration that overhangs the rim effectively increases the model's footprint, and elements that raise the model substantially change its height and line of sight. Both can cause friction at events, and both can make a model harder to store or transport.
The safe approach is to keep everything inside the base edge and keep height increases modest unless you are building a display piece rather than a gaming model. Our basing guide covers schemes that add character without adding footprint.
Frequently asked questions
What is the most common base size?
32mm round accounts for a large share of current infantry, with 25mm round still common on older and smaller models. Beyond that, 40mm, 50mm and 60mm rounds cover most heavier infantry and small vehicles.
Where do I find the correct base size for a specific model?
The base supplied in the current kit is the most reliable indicator. Beyond that, check current official material for the model and, if you are playing competitively, the event organiser's pack. Third-party charts are convenient but go out of date.
Can I use a larger base than the model came with?
Physically yes, but it changes the footprint, and in organised play that is generally not acceptable. In casual play, agree it with your opponent first.
Does base size affect storage?
Considerably. Base diameter determines how many models fit per tray or shelf, and foam trays are cut for specific footprints. Larger and oval bases are the ones most likely to cause storage headaches.
Are third-party bases acceptable?
For casual play, generally yes, provided the diameter is correct. For events, check the organiser's policy. The dimension is what matters; the manufacturer usually does not, but do not assume.
Independent guide published by Blubbercove Ltd/WarSplay. This article is not affiliated with, sponsored by, endorsed by, authorised by or licensed by Games Workshop Limited. Warhammer 40,000 is a trade mark of Games Workshop Limited.