How long should nails be for a nail gun?

As a rule of thumb the nail should pass fully through the top material and penetrate the receiving substrate by about twice the thickness of the piece being fastened — roughly 2x for softwood and panels, and about 1.5x for hardwood (which grips harder). That gives a total nail length of around three times the top thickness. For example, fixing 18mm material into softwood needs about 36mm of penetration, so 18mm + 36mm = 54mm — round up to a standard 63mm nail. Toe nailing and end grain need longer nails because the effective grip is reduced.

What gauge nail gun do I need?

18-gauge (1.2mm) brad nailers are for trim and thin material up to about 12mm. 16-gauge (1.6mm) finish nailers handle most joinery and trim up to about 25mm. 15-gauge (1.8mm) angled finish nailers suit heavier trim, architraves and cabinetry. Finish and brad nailers are trim tools and must not be used for load-bearing connections — structural framing, decking and sheathing need a framing nailer firing ~2.8–3.3mm shank nails (0.113–0.131in), positive-placement nails, or structural screws.

Can I nail into end grain?

End grain has roughly 50% of the holding power of face or edge grain. For structural connections into end grain, use ring shank nails, add adhesive, or preferably use screws. Non-structural end grain connections (like skirting boards to studs) work fine with standard nails at increased length.

Toe nailing is driving nails at an angle (typically 30-45 degrees) through one piece into another, used where face nailing is not possible (e.g., studs to sole plate). It requires longer nails than face nailing and typically 3-4 nails per joint for adequate holding. Pre-drilling helps prevent splitting in hardwoods.

Nail Gun Selection Calculator — Correct Nail Length & Gauge

Find the right nail length, gauge, and type for your material and connection. Get holding power estimates and nails-per-joint recommendations.

Top Material Thickness

Thickness of the piece you are fixing through (the top member), in mm

SubstrateThe receiving material the nail anchors into — affects holding power and required penetration

Connection TypeFace = driven perpendicular; Toe = driven at ~30–45° into the receiving member; End grain holds roughly 50% of side grain

Load TypeStructural (load-bearing) connections need framing nails or structural screws — not a finish or brad nailer

How We Calculate This

This calculator determines the minimum nail length based on the top material thickness, required substrate penetration, and connection type. It then recommends nail gauge, type, and quantity based on the application.

Minimum penetration into substrate

Penetration is the depth the nail embeds in the receiving member, as a multiple of the top material thickness (total nail length ≈ top thickness + penetration ≈ 3x top thickness):

Softwood: 2.0x top material thickness
Hardwood: 1.5x top material thickness (denser, grips harder)
Plywood: 2.0x top material thickness
OSB: 2.0x top material thickness — use ring-shank nails; OSB’s weakness is withdrawal capacity, not embedment depth

Connection adjustments

Face nailing: x1.0 (standard)
Toe nailing: x1.3 (angle reduces effective penetration)
End grain: x1.5 (poor withdrawal resistance)

Frequently Asked Questions

Last updated: March 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.

Nail Gun Selection Calculator — Correct Nail Length & Gauge

How We Calculate This

Minimum penetration into substrate

Connection adjustments

Frequently Asked Questions

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