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Thread Pitch Chart

Unified inch threads from 3/8″ to 4″ — coarse (UNC), fine (UNF), and the 12- and 8-thread series (12UN and 8UN) — with threads per inch and pitch for every standard size.

Coarse

UNC

The everyday thread. Faster to assemble, more forgiving of dirt and damage, and the default for hex cap screws and bolts.

Fine

UNF

More threads per inch for finer adjustment and better resistance to loosening. The UNF series runs through 1-1/2″.

Constant pitch

12UN

Twelve threads per inch from 9/16″ up. Above 1-1/2″ it’s the standard fine thread, like 2-12 UN.

Constant pitch

8UN

Eight threads per inch at every size from 1″ up. Common on large studs, anchor bolts, and pressure-vessel bolting.

Threads per inch
Source: ASME B1.1 Unified Inch Screw Threads. — means the series has no standard thread at that size. Pitch = 1 ÷ threads per inch. Working in metric? See the metric thread pitch chart.
3/8″ 7/16″ 1/2″ 9/16″ 5/8″ 3/4″ 7/8″ 1″ 1-1/8″ 1-1/4″ 1-3/8″ 1-1/2″ 1-5/8″ 1-3/4″ 1-7/8″ 2″ 2-1/4″ 2-1/2″ 2-3/4″ 3″ 3-1/4″ 3-1/2″ 3-3/4″ 4″
Size Decimalinches UNCcoarse UNFfine 12UN12-thread 8UN8-thread
3/8″ 0.3750 163/8-16 UNCpitch 0.0625″ 243/8-24 UNFpitch 0.0417″ — —
7/16″ 0.4375 147/16-14 UNCpitch 0.0714″ 207/16-20 UNFpitch 0.0500″ — —
1/2″ 0.5000 131/2-13 UNCpitch 0.0769″ 201/2-20 UNFpitch 0.0500″ — —
9/16″ 0.5625 129/16-12 UNCpitch 0.0833″ 189/16-18 UNFpitch 0.0556″ 129/16-12 UNpitch 0.0833″same as UNC —
5/8″ 0.6250 115/8-11 UNCpitch 0.0909″ 185/8-18 UNFpitch 0.0556″ 125/8-12 UNpitch 0.0833″ —
3/4″ 0.7500 103/4-10 UNCpitch 0.1000″ 163/4-16 UNFpitch 0.0625″ 123/4-12 UNpitch 0.0833″ —
7/8″ 0.8750 97/8-9 UNCpitch 0.1111″ 147/8-14 UNFpitch 0.0714″ 127/8-12 UNpitch 0.0833″ —
1″ 1.0000 81-8 UNCpitch 0.1250″ 121-12 UNFpitch 0.0833″ 121-12 UNpitch 0.0833″same as UNF 81-8 UNpitch 0.1250″same as UNC
1-1/8″ 1.1250 71-1/8-7 UNCpitch 0.1429″ 121-1/8-12 UNFpitch 0.0833″ 121-1/8-12 UNpitch 0.0833″same as UNF 81-1/8-8 UNpitch 0.1250″
1-1/4″ 1.2500 71-1/4-7 UNCpitch 0.1429″ 121-1/4-12 UNFpitch 0.0833″ 121-1/4-12 UNpitch 0.0833″same as UNF 81-1/4-8 UNpitch 0.1250″
1-3/8″ 1.3750 61-3/8-6 UNCpitch 0.1667″ 121-3/8-12 UNFpitch 0.0833″ 121-3/8-12 UNpitch 0.0833″same as UNF 81-3/8-8 UNpitch 0.1250″
1-1/2″ 1.5000 61-1/2-6 UNCpitch 0.1667″ 121-1/2-12 UNFpitch 0.0833″ 121-1/2-12 UNpitch 0.0833″same as UNF 81-1/2-8 UNpitch 0.1250″
1-5/8″ 1.6250 — — 121-5/8-12 UNpitch 0.0833″ 81-5/8-8 UNpitch 0.1250″
1-3/4″ 1.7500 51-3/4-5 UNCpitch 0.2000″ — 121-3/4-12 UNpitch 0.0833″ 81-3/4-8 UNpitch 0.1250″
1-7/8″ 1.8750 — — 121-7/8-12 UNpitch 0.0833″ 81-7/8-8 UNpitch 0.1250″
2″ 2.0000 4.52-4.5 UNCpitch 0.2222″ — 122-12 UNpitch 0.0833″ 82-8 UNpitch 0.1250″
2-1/4″ 2.2500 4.52-1/4-4.5 UNCpitch 0.2222″ — 122-1/4-12 UNpitch 0.0833″ 82-1/4-8 UNpitch 0.1250″
2-1/2″ 2.5000 42-1/2-4 UNCpitch 0.2500″ — 122-1/2-12 UNpitch 0.0833″ 82-1/2-8 UNpitch 0.1250″
2-3/4″ 2.7500 42-3/4-4 UNCpitch 0.2500″ — 122-3/4-12 UNpitch 0.0833″ 82-3/4-8 UNpitch 0.1250″
3″ 3.0000 43-4 UNCpitch 0.2500″ — 123-12 UNpitch 0.0833″ 83-8 UNpitch 0.1250″
3-1/4″ 3.2500 43-1/4-4 UNCpitch 0.2500″ — 123-1/4-12 UNpitch 0.0833″ 83-1/4-8 UNpitch 0.1250″
3-1/2″ 3.5000 43-1/2-4 UNCpitch 0.2500″ — 123-1/2-12 UNpitch 0.0833″ 83-1/2-8 UNpitch 0.1250″
3-3/4″ 3.7500 43-3/4-4 UNCpitch 0.2500″ — 123-3/4-12 UNpitch 0.0833″ 83-3/4-8 UNpitch 0.1250″
4″ 4.0000 44-4 UNCpitch 0.2500″ — 124-12 UNpitch 0.0833″ 84-8 UNpitch 0.1250″

The UNF series ends at 1-1/2″; above that, the usual fine thread is 12UN, for example 2-12 UN. “Same as” marks a size where the 12- or 8-thread pitch is already that size’s UNC or UNF thread. 1-5/8″ and 1-7/8″ have no UNC thread; they are made in 12UN and 8UN. Reference information only — verify against the current published standard before use.