M3
Metric5.5 mm / 0.2165 in
Finder
Wrench Size Finder
Search by bolt size or enter a measured width across flats. The finder returns the likely metric or SAE wrench/socket size and the actual A/F dimension in both unit systems.
Best match
Metric
16 mm
For M10 hex
- Across flats
- 16 mm / 0.6299 in
- Bolt size
- M10
Matching wrench sizes
Older metric standards can use different hex sizes. Measure legacy hardware.
M4
Metric7 mm / 0.2756 in
M5
Metric8 mm / 0.315 in
M6
Metric10 mm / 0.3937 in
M8
Metric13 mm / 0.5118 in
M10
Metric16 mm / 0.6299 in
M12
Metric18 mm / 0.7087 in
M14
Metric21 mm / 0.8268 in
Thread size is not wrench size
Wrench size is the hex width across flats, not the bolt's nominal thread diameter. An M10 thread commonly takes a 16 mm wrench under current ISO values. For the static table, use the wrench size chart.