What this tool answers
You need a first-pass rivet-nut (rivnut) hand-tool kit before buying. The calculator takes the largest listed metric M size you need, then names the smallest class on this site’s ladder (6, 10, or 12) that covers that size. It is not a fastener certification, grip-range lab test, or substitute for manufacturer instructions.
Listed metric sizes only
Accepted inputs are integer M sizes: 3, 4, 5, 6, 8, 10, and 12. Zero and unlisted sizes (for example 7) return validation errors with no purchase CTA. There is no NO_MATCH path for listed sizes because M12 is the class ceiling.
Class ladder on this site
Classes are returned as max metric M ceilings: 6 (9 in kit · max M6), 10 (14 in · max M10), and 12 (16 in · max M12). The tool picks the smallest class whose ceiling is greater than or equal to metric_mm.
Mandrels and SAE coverage
Kits include mixed metric and SAE mandrels. Confirm the live listing includes every size you will install before you buy. This site does not invent mandrel lists beyond the published product pages.
Grip range and sheet thickness
Match rivet-nut grip range to the sheet thickness you are joining. An undersized or oversized grip can leave a weak set. Check the rivet-nut package grip range separately from the tool class.
Eye protection and shop practice
Wear eye protection when setting rivet nuts. Keep fingers clear of the mandrel and work piece. This site does not certify shop setups or material suitability.
Why there is no NO_MATCH for listed sizes
Every listed metric size (through M12) maps to a published class. Larger than M12 is outside this consumer ladder and is rejected as an unlisted/out-of-range validation case rather than a purchase NO_MATCH CTA path.
Sources
Shop practice of sizing rivnut tools to the largest metric fastener needed. Manufacturer safety culture around rated hand tools and PPE. VEVOR US rivet-nut tool product pages for kit classes dated in products.json (checked 2026-09-10).