180 cm ÷ 175 cm ≈ 1.029
A unitless number. A ratio of 1 means equal lengths; above 1 means your arm span is longer.
Unit changes preserve your original measurements. Displayed values are rounded.
Example result
Ratio
1.029arm span ÷ height
Difference
+5 cm+1.97 inches
Your arm span is longer than your height.
Shared baseline · centimeters
Understand your proportions
Ape index calculator
Your ape index compares your arm span with your height. Enter both measurements above to calculate the arm span to height ratio and the difference in centimeters and inches. Arm span, sometimes called wingspan, is the full distance from one fingertip to the other.
Two ways to calculate
What is the ape index formula?
Ape index is reported in two ways: a ratio or a signed difference. Both describe the same pair of measurements, but their numbers mean different things. Always check which formula a result uses.
Use the same unit for arm span and height before calculating. The calculator converts feet and inches using exactly 2.54 cm per inch. Results are rounded for display, after the calculation.
To express the difference as a percentage of height, subtract 1 from the ratio and multiply by 100. For example, 1.04 means your arm span is 4% longer than your height. To find the difference in length instead, multiply your height by (ratio − 1). A ratio of 1.04 does not mean a difference of 4 cm.
180 cm − 175 cm = +5 cm ≈ +1.97 in
A signed length. Keep the unit: +5 cm and +5 inches are different results.
Start with two measurements
How to measure height and arm span (wingspan)
Use a tape measure and a flat wall. A second person makes it easier to keep the tape level and read both endpoints.
01 · Standing height
- Take off your shoes and stand upright on a firm, level floor with your back against a wall.
- Look straight ahead. Keep your heels down and avoid tilting your head upward.
- Place a flat book level on the crown of your head and mark its lower edge on the wall.
- Measure vertically from the floor to that mark.
02 · Arm span
- Stand with your back against a wall and extend both arms sideways at shoulder height.
- Keep your elbows and fingers straight, with your arms horizontal.
- Have a helper measure in a straight line from the tip of one middle finger to the tip of the other.
- Repeat the measurement to check it. Keep the tape straight instead of following your body's contours.
Arm span is different from one-arm reach
Wingspan includes both arms and the width between your shoulders. Measuring from your shoulder to one fingertip gives a different length, so do not enter that number or simply double it. Standing reach, measured from the floor to an overhead fingertip, also uses different endpoints. Use the horizontal fingertip-to-fingertip measurement shown above for this calculator.
Read the result
Positive, zero or negative?
The sign describes how your arm span compares with your height. It does not rank you against other people.
Positive difference
Your arm span is longer than your height. At 175 cm tall with a 180 cm arm span, the difference is +5 cm.
Zero difference
Your arm span and height are equal. A ratio of 1 and a difference of 0 describe the same relationship.
Negative difference
Your arm span is shorter than your height. At 180 cm tall with a 175 cm arm span, the difference is −5 cm.
Worked examples
Ape index chart: what do 1.04, 1.06 and 1.08 mean?
These examples use the same height so you can compare ratios with actual lengths. They are calculated examples, not population averages or athletic targets.
| Ape index ratio | Arm span | Difference |
|---|---|---|
| 0.98 | 171.5 cm | −3.5 cm |
| 1.00 | 175 cm | 0 cm |
| 1.04 | 182 cm | +7 cm |
| 1.06 | 185.5 cm | +10.5 cm |
| 1.08 | 189 cm | +14 cm |
An ape index of 1.06 means arm span is 106% of height, or 6% longer; 1.08 means it is 8% longer. Neither number tells you the difference in centimeters until you include the person's height.
Two people can have the same ratio and different arm spans. At 160 cm tall, a ratio of 1.04 corresponds to 166.4 cm of arm span and a +6.4 cm difference. At 190 cm tall, the same ratio corresponds to 197.6 cm and +7.6 cm. Enter your own measured lengths in the calculator for your result; do not use this table to estimate an unmeasured arm span.
Reference point
Is an ape index of 1 the average?
A ratio of 1 and a difference of 0 are the mathematical reference points for equal arm span and height. That definition does not establish the average for a population. An average must come from measurements of a defined group, with information about who was measured and how.
This calculator does not use a population reference dataset, so it does not assign an average range or percentile. A ratio of 1.04 means 4% longer than your own height, not 4% above the population average. Results from a small group of climbers cannot establish a reference range for everyone. Read your result as a comparison of your two measurements, not a health classification.
Climbing context
Does ape index predict climbing ability?
Ape index describes one body proportion. It does not measure how strongly you can hold a grip, how long you can sustain an effort, or how you move between holds. It also does not give your absolute reach: as the examples above show, height still matters when translating a ratio into a length.
Laffaye and colleagues' study of 41 climbers compared novice, skilled and elite groups, measuring body dimensions alongside general and climbing-specific strength and endurance. Their model linked climbing ability more closely to trainable strength factors than to body dimensions. It was a study of that sample, not a universal formula for predicting a person's climbing grade from an ape index.
There is no pass/fail score in this tool. A positive difference does not guarantee success on a climb, and a negative difference is not a verdict on your potential. Use the number to describe your proportions consistently, including the formula and units when you share it.
Common questions
About your ape index
Is a 1.04 ape index good?
It means your arm span is 4% longer than your height. For someone 175 cm tall, that is 182 cm of arm span and a +7 cm difference. Whether it helps with a particular task cannot be judged from the ratio alone. The climbing explanation above describes why this calculator does not give a good/bad score.
Why do two calculators show different ape index numbers?
Check the formula and units before comparing results. A height of 175 cm and arm span of 180 cm give a ratio of about 1.029, a difference of +5 cm, or a difference of about +1.97 inches. All three describe the same measurements. If the formula and units match, check whether the inputs or displayed result were rounded.
Does switching between cm and inches change the ratio?
No. Converting both measurements by the same factor leaves the ratio unchanged. The difference has a different numerical value because it has units: +5.08 cm is +2 inches. Small rounding differences can appear in the displayed inputs.
Is wingspan the same as arm span?
For this calculator, yes. Both mean the full fingertip-to-fingertip measurement across your outstretched arms. Do not enter the length of just one arm or the distance between your shoulders.
Can I calculate ape index from height alone?
No. You need your measured arm span as well as your height. Assuming the two are equal would always produce a ratio of 1 and a difference of 0, regardless of your actual proportions.
Why might two measurements give slightly different results?
Bent elbows, a sloping tape, shoes or a different head position can change the readings. Repeat both measurements using the same method. At a fixed height of 175 cm, a 1 cm change in measured arm span changes the ratio by about 0.006. Near equal lengths, a small measurement difference can even change the sign. More decimal places on the result do not make the original measurements more accurate.
Method & sources
What this calculator uses
The calculation uses only the two lengths you enter. The measurement reference below defines the ratio as arm span divided by height and describes standing height and horizontal arm span measurements.
The diagrams are measurement guides. The result chart draws both lengths on one scale; it is not a model of your body. No population percentile, health assessment or athlete comparison is calculated.