Drywall Screw Size Chart: Pick the Right Length & Gauge

What does 1/2 in drywall taking a 1-1/4 in #6 screw mean?

On the default — 1/2 in drywall — the screw is 1-1/4 in, #6 gauge (31.75 mm). The millimetres are the inches times 25.4: 1.25 × 25.4 = 31.75 mm. A 1-1/4 in screw through 1/2 in of drywall bites 3/4 in into the stud — past the 5/8 in minimum — so the board holds. Whether that is the right screw depends on the stud — a screw into a split stud holds nothing, whatever its length.

Three things about the model are worth stating plainly.

First, the conversion is 1.25 × 25.4 = 31.75 mm, and the screw is 1-1/4 in #6 — the millimetres and the screw are two outputs, never the same number. Second, the meaning is 1-1/4 in of screw for 1/2 in of drywall — the screw that bites 3/4 in into the stud, not the thickness of the board. And third, the screw is a step function of the thickness band: 0.5 in takes a 1-1/4 in screw, but 0.51 in takes a 1-5/8 in screw — one hundredth of an inch crosses the band — all listed in Accuracy & limitations.

The full chart

1/4 in drywall: 1 in #6 screw (25.40 mm) — The thinnest drywall — a 1 in #6 screw, for 1/4 in board.

3/8 in drywall: 1-1/8 in #6 screw (28.58 mm) — A 1-1/8 in #6 screw, for 3/8 in board.

1/2 in drywall: 1-1/4 in #6 screw (31.75 mm) — The standard — a 1-1/4 in #6 screw, for 1/2 in board.

5/8 in drywall: 1-5/8 in #6 screw (41.28 mm) — A 1-5/8 in #6 screw, for 5/8 in board — the thickest single layer.

3/4 in drywall: 2 in #8 screw (50.80 mm) — A 2 in #8 screw, for double 3/8 in board.

1 in drywall: 2-1/2 in #8 screw (63.50 mm) — A 2-1/2 in #8 screw, for double 1/2 in board.

1-1/4 in drywall: 3 in #8 screw (76.20 mm) — The longest — a 3 in #8 screw, for double 5/8 in board.

The worked example, line by line

Setup: drywall thickness 1/2 in.

Line 1 — the band. 1/2 in is the third row of the chart — the standard thickness.

Line 2 — the screw length. The third row gives 1-1/4 in.

Line 3 — the gauge. The third row gives #6 — the gauge for single-layer drywall.

Line 4 — the millimetres. 1.25 × 25.4 = 31.75 mm.

Line 5 — the bite. 1-1/4 in minus 1/2 in of drywall leaves 3/4 in biting into the stud — past the 5/8 in minimum.

Line 6 — the check. At 0.51 in the screw is 1-5/8 in — one hundredth of an inch crosses the band; and at 0.49 in it is still 1-1/4 in.

Every branch, checked

Thin drywall: 1/4 in drywall: 1 in #6 screw (25.40 mm) — single layer of 1/4 in drywall; 3/8 in drywall: 1-1/8 in #6 screw (28.58 mm) — single layer of 3/8 in drywall; 1/2 in drywall: 1-1/4 in #6 screw (31.75 mm) — single layer of 1/2 in drywall

Thick drywall: 5/8 in drywall: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall; 3/4 in drywall: 2 in #8 screw (50.80 mm) — double layer of 3/8 in drywall; 1 in drywall: 2-1/2 in #8 screw (63.50 mm) — double layer of 1/2 in drywall; 1-1/4 in drywall: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall

#6 gauge: 1/4 in drywall: 1 in #6 screw (25.40 mm) — single layer of 1/4 in drywall; 3/8 in drywall: 1-1/8 in #6 screw (28.58 mm) — single layer of 3/8 in drywall; 1/2 in drywall: 1-1/4 in #6 screw (31.75 mm) — single layer of 1/2 in drywall; 5/8 in drywall: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall

#8 gauge: 3/4 in drywall: 2 in #8 screw (50.80 mm) — double layer of 3/8 in drywall; 1 in drywall: 2-1/2 in #8 screw (63.50 mm) — double layer of 1/2 in drywall; 1-1/4 in drywall: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall

1/2 in drywall: Drywall 1/2 in thick: 1-1/4 in #6 screw (31.75 mm)

5/8 in drywall: Drywall 5/8 in thick: 1-5/8 in #6 screw (41.28 mm)

Double 1/2 in drywall: Drywall 1 in thick: 2-1/2 in #8 screw (63.50 mm)

The reverses, worked backwards

Largest thickness for a 1 in screw: At the displayed 1/4 in the figures are Drywall 1/4 in thick: 1 in #6 screw (25.40 mm) — single layer of 1/4 in drywall. At 0.26 in the figures are Drywall 0.26 in thick: 1-1/8 in #6 screw (28.58 mm) — single layer of 3/8 in drywall — a 1-1/8 in screw — so 1/4 in is the largest thickness for a 1 in screw.

Largest thickness for a 1-1/8 in screw: At the displayed 3/8 in the figures are Drywall 3/8 in thick: 1-1/8 in #6 screw (28.58 mm) — single layer of 3/8 in drywall. At 0.38 in the figures are Drywall 0.38 in thick: 1-1/4 in #6 screw (31.75 mm) — single layer of 1/2 in drywall — a 1-1/4 in screw — so 3/8 in is the largest thickness for a 1-1/8 in screw.

Largest thickness for a 1-1/4 in screw: At the displayed 1/2 in the figures are Drywall 1/2 in thick: 1-1/4 in #6 screw (31.75 mm) — single layer of 1/2 in drywall. At 0.51 in the figures are Drywall 0.51 in thick: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall — a 1-5/8 in screw — so 1/2 in is the largest thickness for a 1-1/4 in screw.

Largest thickness for a 1-5/8 in screw: At the displayed 5/8 in the figures are Drywall 5/8 in thick: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall. At 0.63 in the figures are Drywall 0.63 in thick: 2 in #8 screw (50.80 mm) — double layer of 3/8 in drywall — a 2 in screw — so 5/8 in is the largest thickness for a 1-5/8 in screw.

Largest thickness for a 2 in screw: At the displayed 3/4 in the figures are Drywall 3/4 in thick: 2 in #8 screw (50.80 mm) — double layer of 3/8 in drywall. At 0.76 in the figures are Drywall 0.76 in thick: 2-1/2 in #8 screw (63.50 mm) — double layer of 1/2 in drywall — a 2-1/2 in screw — so 3/4 in is the largest thickness for a 2 in screw.

Largest thickness for a 2-1/2 in screw: At the displayed 1 in the figures are Drywall 1 in thick: 2-1/2 in #8 screw (63.50 mm) — double layer of 1/2 in drywall. At 1.01 in the figures are Drywall 1.01 in thick: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall — a 3 in screw — so 1 in is the largest thickness for a 2-1/2 in screw.

A warning about the neighbours: every neighbour above sits one hundredth of an inch from the star, and every neighbour figure is a different screw even though the thickness barely moved — the band, not the exact thickness, decides. The page prints the full chart so the rounding does not mislead you: R1 1/4 in / 0.26 in; R2 3/8 in / 0.38 in; R3 1/2 in / 0.51 in; R4 5/8 in / 0.63 in; R5 3/4 in / 0.76 in; R6 1 in / 1.01 in.

What the defaults assume

The defaults are 1/2 in drywall — Drywall 1/2 in thick: 1-1/4 in #6 screw (31.75 mm). With Thin drywall, 1/4 in drywall: 1 in #6 screw (25.40 mm) — single layer of 1/4 in drywall; 3/8 in drywall: 1-1/8 in #6 screw (28.58 mm) — single layer of 3/8 in drywall; 1/2 in drywall: 1-1/4 in #6 screw (31.75 mm) — single layer of 1/2 in drywall. With Thick drywall, 5/8 in drywall: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall; 3/4 in drywall: 2 in #8 screw (50.80 mm) — double layer of 3/8 in drywall; 1 in drywall: 2-1/2 in #8 screw (63.50 mm) — double layer of 1/2 in drywall; 1-1/4 in drywall: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall. With #6 gauge, 1/4 in drywall: 1 in #6 screw (25.40 mm) — single layer of 1/4 in drywall; 3/8 in drywall: 1-1/8 in #6 screw (28.58 mm) — single layer of 3/8 in drywall; 1/2 in drywall: 1-1/4 in #6 screw (31.75 mm) — single layer of 1/2 in drywall; 5/8 in drywall: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall. With #8 gauge, 3/4 in drywall: 2 in #8 screw (50.80 mm) — double layer of 3/8 in drywall; 1 in drywall: 2-1/2 in #8 screw (63.50 mm) — double layer of 1/2 in drywall; 1-1/4 in drywall: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall. With 1/2 in drywall, Drywall 1/2 in thick: 1-1/4 in #6 screw (31.75 mm). With 5/8 in drywall, Drywall 5/8 in thick: 1-5/8 in #6 screw (41.28 mm). With Double 1/2 in drywall, Drywall 1 in thick: 2-1/2 in #8 screw (63.50 mm). With Thickness 0 in, Enter your drywall thickness in inches. — no thickness to size for — the calculator says so plainly. With Thickness 0.47 in, Drywall 0.47 in thick: 1-1/4 in #6 screw (31.75 mm) — single layer of 1/2 in drywall — between rows — the band, not the exact thickness, decides. With Thickness 1.5 in, Drywall 1.5 in thick: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall — above the table — the table tops out at the 3 in #8 screw. With Thickness 0.2 in, Drywall 0.2 in thick: 1 in #6 screw (25.40 mm) — single layer of 1/4 in drywall — the thinnest band — a 1 in #6 screw. With Thickness 0.7 in, Drywall 0.7 in thick: 2 in #8 screw (50.80 mm) — double layer of 3/8 in drywall — a double layer in disguise — a 2 in #8 screw. With Thickness 0.9 in, Drywall 0.9 in thick: 2-1/2 in #8 screw (63.50 mm) — double layer of 1/2 in drywall — double 1/2 in drywall — a 2-1/2 in #8 screw. With Thickness 1.2 in, Drywall 1.2 in thick: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall — double 5/8 in drywall — a 3 in #8 screw. With Thickness 0.1 in, Drywall 0.1 in thick: 1 in #6 screw (25.40 mm) — single layer of 1/4 in drywall — the thinnest drywall there is — a 1 in #6 screw. With Thickness 0.625 in, Drywall 5/8 in thick: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall — the band edge itself — a 1-5/8 in #6 screw. With Thickness 2 in, Drywall 2 in thick: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall — far above the table — the table tops out at the 3 in #8 screw. With Thickness 0.55 in, Drywall 0.55 in thick: 1-5/8 in #6 screw (41.28 mm) — single layer of 5/8 in drywall — between rows — the band, not the exact thickness, decides. With Thickness 1.26 in, Drywall 1.26 in thick: 3 in #8 screw (76.20 mm) — double layer of 5/8 in drywall — just over the top band — a 3 in #8 screw.

A note on the rounding: the millimetres are displayed to two decimals, half-up. A 1-1/8 in screw is 28.575 mm unrounded — it displays as 28.58 mm — and a 1-5/8 in screw is 41.275 mm unrounded — it displays as 41.28 mm. Plain JavaScript toFixed(2) gives 28.57 and 41.27, so the calculator uses the half-up path and the page prints the half-up figures. A 1-1/4 in screw is 31.75 mm, a 2-1/2 in screw is 63.50 mm and a 3 in screw is 76.20 mm. The page prints the unrounded values where they differ so the rounding does not mislead you.

Output · formula · meaning

Who uses this

• The homeowner hanging a new wall: they learn 1/2 in drywall takes a 1-1/4 in #6 screw — and they check the 5/8 in row to see the screw for the thicker fire-rated board.
• The DIYer fixing a hole: they learn the screw must bite 5/8 in into the stud — and they check the 0.47 in edge to see that a slightly thin board still takes the same screw.
• The contractor pricing a job: they learn double 1/2 in drywall takes a 2-1/2 in #8 screw — and they check the 1.26 in edge to see that anything thicker tops out at 3 in.
• The renter mounting a shelf: they learn the screw length by the board, not by the shelf — and they check the 1/4 in row to see the screw for the thinnest board.

Accuracy & limitations

The math is first-principles: the millimetres are the inches times 25.4, and the screw is the first standard size at or above the band for that thickness — all in inches and millimetres, the millimetres displayed to two decimals half-up. There IS a division in this chart — none at all: the screw is a table lookup, so there is nothing undefined except a thickness of zero, where the calculator says so plainly. At 0 in there is no drywall to size for, so there is no screw — and the calculator says so. At 1.5 in the table tops out at the 3 in #8 screw — the longest standard drywall screw — and the calculator says so. A 1-1/8 in screw is 28.575 mm unrounded — it displays as 28.58 mm — and a 1-5/8 in screw is 41.275 mm unrounded — it displays as 41.28 mm. The largest thickness for a 1-1/4 in screw is 1/2 in — the page shows the displayed 1/2 in input only, and the forward at that input is a 1-1/4 in #6 screw (31.75 mm). What the model cannot do is say whether the stud is sound: it says nothing about the wood — whether the stud is split, damp or metal — and it says nothing about the thread — coarse-thread screws for wood studs, fine-thread screws for metal studs. Use it to see the screw — then check the screw size chart and the drywall calculator before you buy the box.

Frequently asked questions