About the Nut Size Calculator
Spanner size, height and washer dimensions for standard metric nuts.
Also known as: spanner size, wrench size for bolt, nut dimensions, hex size chart.
How to use this calculator
- Enter thread size.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Across corners = across flats × 2/√3
Worked example
Using the values pre-filled in the calculator above:
- Thread size: M10
the calculator returns:
- Spanner size (across flats): 16 mm
- Across corners: 18.48 mm
- Nut height: 8.4 mm
- Washer outside diameter: 20 mm