There are several ways to find your grip size:
1. Experiment. Take a tool you already own that has a handle that feels too small and put a few wraps of duct tape around the handle in the place where you hold it the most. Use the tool for a day. Keep adding tape until it starts to feel too large, and then remove a few wraps until it is comfortable. Wrap a tape measure around the area that you’ve taped to find the grip size that works best for you.
2. Measure your hand's grip diameter and use it to calculate your grip size.
- Use your hand size. 20% of your hand length equals your grip diameter. EXAMPLE: 20% of a 7-1/4" (or 7.25") hand length equals about 1-1/2" (calculated as follows: 7.25" x 0.20 = 1.45" --rounds up to 1.5")
- Use the "OK" test. Make the okay sign using your thumb and index finger and then measure the inside of the "O" formed to find the diameter. In photo 2, for example, the hand diameter is about 1-1/2" (or 1.5").
Once you know your hand's grip diameter, you can calculate your grip size by multiplying your grip diameter by 3.14. EXAMPLE: A hand with a grip diameter of 1-1/2" (or 1.5") would have a grip size of roughly 4-3/4" (calculated as follows: 1.5" x 3.14 = 4.7").
3. Rely on the research. The National Institute for Occupational Safety and Health (NIOSH) suggests a grip diameter range of between 1-1/4" to 2". These measures are equal to grip sizes of roughly 3.9" to 6.3" for a "power grip." If the length of your hand is on the larger size, go for the higher grip size. If the length of your hand is on the smaller size, go with a lower grip size.
There are two easy to use online calculators that can help:
"Calculating the Area of Circles - Online Calculator" calculates your grip size (the circumference) -- just enter your hand diameter and click "solve the others".
"Fraction Decimal Calculator With Equivalents Table" quickly translate decimal points to fractions or fractions to decimal points.
Grip span. Your grip span is the distance between the thumb and fingers when the tool jaws are open or closed.
To calculate your strongest grip span, measure your hand while spread wide open from the tip of your thumb to the tip of your little finger in centimeters (cm) (photo 3), divide that number by 5, and add 1.5 cm. For example, if your open hand size from the tip of the little finger to the tip of the thumb is 18 cm, then your strongest grip would be about 5.1 cm or 2" (Calculation: 18 cm divided by 5 = 3.6 cm; 3.6 cm + 1.5 cm = 5.1 cm or about 2".) (This online Metric Conversion calculator easily converts centimeters to inches.)