Pressure belongs on the glue face, not on the finished panel. Enter the glued length and the glued width — stock thickness on an edge joint — pick a target psi, and the calculator returns total pounds plus a clamp count from the rating on your clamps. Layout arithmetic only. Not a glue data sheet.
Pressure belongs on the glue face, not on the finished panel.
Use it when planning a glue-up — an edge-joined top, a laminated beam, a bent lamination — to work out the total clamping force the joint needs and roughly how many clamps that takes. Measure the glue face itself (joint length × stock thickness for an edge joint), pick a pressure suited to the species, and compare the result with what your clamps can deliver.
The glue face is a rectangle: length along the joint times the width of that face. On an edge glue-up the width is the thickness of the stock, not the width of the finished panel. Multiply that area by the target pressure to get total clamp force in pounds. Divide by the rating of one clamp and round up.
A = length × width (in² of glue face)
F = A × psi (lbf of total clamp force)
n = ceil(F ÷ clamp rating)
An 8 × 24 in panel that is 1½ in thick is the board you are building. It is not the glue face unless you are laminating those two faces together. Two ¾ in boards meeting on a 12 in edge are 12 × 0.75 = 9 in². Put 8 × 24 in the calculator and you invent a tabletop of glue and tens of thousands of pounds. This page does not choose a glue, an open time, or a caul pattern. Read the bottle you bought.
| Glue face | psi | Force | 400 lb clamps |
|---|---|---|---|
| 12 × 0.75 in (9 in²) | 150 | 1,350 lbf | 4 |
| 12 × 0.75 in | 125 | 1,125 lbf | 3 |
| 24 × 0.75 in | 150 | 2,700 lbf | 7 |
| 24 × 1.5 in | 200 | 7,200 lbf | 18 |
| 8 × 24 in panel face (wrong) | 150 | 28,800 lbf | 72 |
Those rows come from F = A × psi and n = ceil(F / 400). The shop check is the first row: 12 in × 0.75 in = 9 in² at 150 psi is 1,350 lbf, which is four 400 lb clamps. The last row is the panel-face mistake — leave it in the table so it is obvious.
The glue face. For boards edge-glued into a panel, that is joint length times stock thickness. A 12 in edge on ¾ in stock is 9 in². An 8 × 24 in panel 1½ in thick is the finished piece. Only use 8 × 24 if those two faces are the surfaces you are gluing together (a face lamination), which is a different job.
The usual shop band for PVA on pine, fir, and similar is about 100–150 psi. This calculator defaults to 125, the middle of that band. The top of the band is 150 — type it under Custom for the 9 in² / 1,350 lbf check. Medium-density stock is 175. Hardwood is 200 here. Some sheets run hardwood toward 250; that is a bottle and species call, not a number this page invents as a spec.
No. The rating is the force the maker claims at a stated tightening, printed on the clamp or in its sheet. Hand tightness is not a calibrated load cell. This count assumes every clamp actually delivers that rating and that they share the load. If the stamp is missing, a conservative shop number is better than a guess from a catalog photo. Cauls still matter: one clamp in the middle of a 24 in edge does not print 400 lbf evenly along the joint.
Four, if each clamp is a 400 lb rating: 9 × 150 = 1,350, and ceil(1,350 ÷ 400) = 4. At the default 125 psi the same face is 1,125 lbf and three of those clamps. Alternate above and below on a panel glue-up so the assembly stays flat. The count is from total force, not a spacing table.
No. Open time, bottle temperature, starved joints, and species are on the adhesive sheet. This is layout: area, a target psi, and a rounded-up clamp count. Squeeze-out is a glue-up signal, not a number this calculator reports.
Use the unit you measured. Millimetres are converted to square inches before the psi multiply, because psi is pounds per square inch. The clamp rating stays in pounds-force. Mixing a 12 on the length with a 19 on the width because you meant 19 mm will invent a slab.