When it comes to the tensile strength of wire, there are two important values: "yield strength," which is the stress at which a material begins to permanently deform, and "ultimate strength," which is the maximum amount of stress a material can withstand without breaking. Determined in a laboratory, tensile strength is expressed in units of pressure (typically megapascals, or "MPa").

To calculate the yield strength and ultimate strength of a wire, you must multiply its cross sectional area (which can be derived from its diameter, or "gauge") by the specific tensile strengths of its material.

- Visit www.engineeringtoolbox.com/awg-wire-gauge-d_731.html and look up the wire's gauge number in the far left column.
- Scan right across the gauge number's row to find out the thickness of the wire (in millimeters). Write down this number.
- Continue scanning across the row to find out the cross sectional area of the wire (in square millimeters).
- Visit www.matweb.com/search/search.aspx. Type "wire" into the text field next to the "Search" button. Click "Search."
- Locate the specific wire you're trying to evaluate and click on its name to display its technical data. The measurements in these wires' names (e.g. "2.3 mm wire" or "4 mm wire") refer to the wire's thickness. Therefore, refer to the value you wrote down in Step 2.
- Once the wire's technical data page has loaded, look under the heading "Mechanical Properties."
- Write down the yield strength and ultimate strength values from the "Metric" column (in MPa).
- Multiply each of these values by 1,000,000 to convert their units to pascals (Pa).
- Multiply the wire's cross sectional area (see Step 3) by 0.000001 to convert its units to square meters.
- Multiply this product by the yield strength (in pascals) from Step 8. The result is the minimum amount of force (in Newtons) need to permanently deform the wire.
- Multiply the cross section area (in square meters, from Step 9) by the ultimate strength (in pascals, from Step 8) to determine the maximum force (in Newtons) the wire can support without breaking.