What this tool answers
You need a first-pass F-clamp size before buying a pack. Enter maximum opening in inches. The calculator names the smallest class on this site’s ladder — 6, 12, 24, or 36 in — or returns NO_MATCH. It is not a glue-pressure calculation, fixture design, or pipe-clamp selector.
Opening vs throat depth
Opening is how wide the jaws can span along the bar. Throat depth is how far the screw reaches from the bar toward the center of the workpiece. Both matter for glue-ups and edge work. This screen matches opening only — always confirm throat on the product page.
Class ladder on this site
Classes use published VEVOR US F-clamp openings checked 2026-09-10: 6 in, 12 in, 24 in, and 36 in. Matching rule: smallest class where published opening ≥ needed opening.
When the answer is NO_MATCH
If needed opening exceeds 36 in, this site returns NO_MATCH. Typical next steps: use a longer bar or pipe clamp, split the glue-up, or change the fixture. Do not force a 36 in F-clamp past this screen.
Load rating and pads
Capacity alone is not enough. Confirm labeled load limit and whether soft pads are included. Never use an F-clamp as a structural hoist or welding hold-down beyond the nameplate.
Sources
VEVOR US F-clamp product pages for opening claims (checked 2026-09-10). Consumer practice separating F-bar clamps from pipe clamps and C-clamps. Safety framing follows common manufacturer warnings on load rating and hand clearance.