[Glossary](/glossary.md)/[Armor](/glossary/category/armor.md)

# Overmatch

The rule that a shell with a caliber at least three times a plate's thickness cannot ricochet off it, no matter the angle.

Also known as 3 caliber rule, overmatching.

Overmatch is why large-caliber guns ignore [armor](/glossary/armor-thickness.md) that stops smaller ones. A 122 millimetre [shell](/glossary/shell.md) overmatches any plate up to about 40 millimetres, so a sloped 30 millimetre roof or a thin angled side is defeated as if it were flat.

It has two consequences: the [ricochet](/glossary/ricochet.md) check is skipped entirely, and [normalization](/glossary/normalization.md) is amplified, so the [effective thickness](/glossary/effective-armor.md) collapses toward the nominal value.

This is what makes the difference between a 105 and a 122 millimetre gun larger than their [penetration](/glossary/penetration.md) figures suggest, and why the thickness of a [light tank](/glossary/light-tank.md)'s upper plate is chosen so carefully against the [calibers](/glossary/caliber.md) it will meet.

## Related terms

[RicochetA shell deflecting off a plate without any penetration check, which happens beyond 70 degrees for most shells and 85 for HEAT.](/glossary/ricochet.md)[CaliberThe diameter of a gun's shell in millimetres, which sets what armor it can overmatch as well as roughly how hard it hits.](/glossary/caliber.md)[NormalizationThe few degrees a shell turns toward the perpendicular on impact, reducing the effective armor it has to cross.](/glossary/normalization.md)[Effective armorThe thickness a shell actually has to defeat once the angle of the plate is accounted for, which is what penetration is compared against.](/glossary/effective-armor.md)

[Every World of Tanks term](/glossary.md)

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