Pocket Hole Calculator

Pocket Hole Calculator for picking a Kreg screw from the thinner board and your jig model. It sets fine or coarse thread for the wood and marks where every hole goes on each joint.

Pocket Hole Calculator for Kreg Jig Setups

The Pocket Hole Calculator picks the Kreg screw for a joint from both board thicknesses, your jig model, the wood and whether the project lives indoors. It then lays out how many holes each joint needs and where to mark them.

Enter actual thickness, not the nominal lumber size. A 1x board is 3/4 inch and a 2x4 is 1 1/2 inches, and 3/4 inch plywood is often 23/32 inch. Inches are the default, and the millimeter switch converts every entry.

Results show the screw length and thread, the Kreg part number, holes per joint with spacing, the drill and driver bits, and the thickness range your stock falls in. It suits face frames, cabinet boxes, bookcases, tabletops and 2x4 builds.

Why the Thinner Board Sets the Screw

Kreg's guide on why material thickness matters says to size the screw from the thinner piece when the outside faces sit flush. The calculator takes both thicknesses for that reason and works from the smaller one.

$$T_s=\min (T_p,T_m)$$

Here $T_p$ is the board that gets the pocket and $T_m$ is the mating board. Join a 3/4 inch shelf to a 1 1/2 inch leg and the screw is the 1 1/4 inch size for 3/4 inch stock, not the 2 1/2 inch size for the leg.

Kreg's official jig guide wants the screw to reach at least 1/2 inch into the second piece. A longer screw sized to the thick board would push its tip out the face of the thin one.

Kreg Thickness Ranges and Screw Lengths

Kreg groups stock into four ranges on its jigs, and the screw length follows the range. The one jig-dependent row is the "i" range, where the 720 and 720PRO take a longer screw than the 520PRO.

So a 1 inch board can call for two different screws depending on the jig. The calculator reads the jig you pick, so a 720 owner gets 2 inch screws where a 520 owner gets 1 1/2 inch.

The 1/2 inch plywood row confuses many builders. On a LumberJocks thread, a K5 owner found the screw box saying 1 inch while the jig label said 3/4 inch. The calculator switches to the 3/4 inch screw when you choose sheet goods in that range, so the tip stays inside the ply.

Fine or Coarse Thread, Indoors or Out

Kreg recommends fine thread for hardwoods like oak, maple and walnut, and coarse thread for softwoods, plywood and MDF. The calculator groups poplar with pine and cedar, as many builders do, though some screw charts list it with the hardwoods.

Fine thread stops at 1 1/2 inches. Kreg's answer on its zinc screw page says longer fine screws snapped their heads when driven into hardwood. So 1 1/2 inch oak gets a coarse 2 1/2 inch screw, and the calculator flags the switch.

Kreg's reply also offers a workaround. Drill 1 1/2 inch hardwood at the 3/4 inch setting and drive a 1 1/2 inch fine screw, which leaves roughly 1 inch of bite in the second piece.

Outdoors, the choices narrow further. Kreg's Blue-Kote screws come in coarse thread only. For outdoor hardwood at 3/4 inch, the calculator points to the stainless fine-thread SML-F125S5, which Kreg's stainless screw listing makes in 1 1/4 inch only.

How the Pocket Hole Calculator Spaces Holes

Kreg's pocket-hole FAQ uses three holes on boards up to 10 inches wide, one 1 inch from each end and one centered. Wider panels start 1 inch from each end, with the rest 6 to 8 inches apart.

That same FAQ also says a board up to 3 inches wide needs only one hole. Kreg's spacing tips put two holes side by side even on a 1x2, since a single screw lets the rail pivot. The calculator follows the two-hole advice for anything under 4 inches.

Past 10 inches, the hole count comes from the joint width $W$, the end distance $e$ and the largest spacing you allow, $s_{max}$. The holes then spread evenly between the two end holes.

$$n=\lceil \frac{W-2e}{s_{max}}\rceil +1$$

$$s=\frac{W-2e}{n-1}$$

A 24 inch tabletop edge with holes 1 inch from each end and a 6 inch limit needs five holes at 5.5 inch spacing. Raise the limit to Kreg's 8 inch upper end and it drops to four holes, 7.33 inches apart.

Enter the width of the joint itself, not the length of the board. A 36 inch rail joined across its 3 1/2 inch end is a 3 1/2 inch joint, which gets two holes.

The first hole must sit less than halfway along the joint, or the two end holes would cross. The calculator flags that entry and also caps joint width at 120 inches.

Kreg Mini and Heavy-Duty Setups

The Kreg Mini has no depth gauge, so the collar is measured from the step of the bit with the bit out of the drill. The calculator shows that collar distance and where the Mini sits on the board for the three thicknesses its manual covers.

The HD and XL jigs use #14 screws with a #3 square drive. Kreg's XL screw page notes the XL jig has only two thickness settings, so there are only two screw lengths. The calculator warns when a board falls between those settings.

Settings That Push a Screw Through the Face

Standard Kreg jigs cover stock from about 1/2 to 1 1/2 inches. Below 7/16 inch the calculator stops and points to Kreg's Micro-Pocket guide, and above 1 1/2 inches it points to the HD or XL jig.

Kreg's FAQ says over-driving typically comes from an impact driver or a drill clutch set too high. A standard drill with a low clutch setting stops the screw once the joint is snug.

Setting the jig for the pocket board and forgetting the mating board is a common way to over-drill. Kreg's answer on its XL screw page is to use the thinner board's settings and screw length when the two thicknesses differ.

The calculator also totals screws across every joint, which helps size a box order. Four joints in 1x6 stock at three holes each need 12 screws. The bookcase calculator and drawer box calculator cover the carcass and drawer parts those joints hold together.

Pocket Hole Assembly Questions

Do pocket-hole joints need glue?

Kreg says the screws alone make a strong joint, so glue is optional for most work. It does recommend glue on edge-joined tabletops, where seasonal movement can open small gaps between boards.

Kreg also advises glue on miters, which tend to open at the tips, and exterior glue on outdoor projects. For panels built with pocket holes, the wood movement gap calculator shows how much a wide glue-up moves across the seasons.

Which face should the pocket holes go on?

Kreg rates both faces as equally strong, so the choice comes down to what stays hidden. Pockets go inside a bookcase, where shelves cover them, and outside a kitchen cabinet, where the next cabinet hides them.

Low-cost plywood is the exception. Kreg drills those parts from the outside, because a screw driven from the inside can push soft or void-filled inner plies out through the edge.

Can you use pocket holes in MDF?

Yes, but Kreg's own FAQ gives mixed advice on thread type, naming fine thread in one line and coarse thread for sheet goods in the next. The calculator follows the coarse-thread advice for sheet goods, matching Kreg's grouping of MDF with plywood.

MDF splits and bulges more easily than solid wood. Kreg suggests glue on MDF joints and a gentle drill clutch, since an over-tightened screw can crush the edge.