Quick answer
Ape index = arm span ÷ height. An arm span of 180 cm and a height of 175 cm gives 1.029, a difference of +5 cm.
Enter arm span and height in the same unit. The calculator returns the ratio and difference.
Related tools: Ponderal Index Calculator: Weight relative to the cube of height. BMI Calculator: Find your Body Mass Index (BMI) and weight status. Height Calculator: Convert height between centimeters and feet-and-inches.
How to use the Ape Index Calculator
- Enter arm span (above 0).
- Enter height (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Arm span | A number | > 0 |
| Height | A number | > 0 |
Formula and method
Formula
ape index = arm span ÷ height
IEEE-754 double precision; shown to the decimals indicated.
A ratio above 1 means arm span exceeds height; use the same unit for both. Informational estimate, not medical advice. Talk to a qualified health professional about your own situation.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Arm span = 180; Height = 175.
| Result | Value |
|---|---|
| Ape index | 1.029 |
| Difference | 5 |
Example 2
Inputs: Arm span = 165; Height = 170.
| Result | Value |
|---|---|
| Ape index | 0.971 |
| Difference | -5 |
Example 3
Inputs: Arm span = 172; Height = 172.
| Result | Value |
|---|---|
| Ape index | 1 |
| Difference | 0 |
The first line is the headline result (ape index). Below it the ape Index Calculator lists difference, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
What it indicates
An index above 1 means a longer reach than height. Rock climbers and basketball players often have a positive ape index, which can help with reach. The average adult is close to 1.0, around 1.01 to 1.03 for men.
Measuring
Stand with your back to a wall, arms outstretched, and measure from fingertip to fingertip. Height is measured barefoot. The index is a curiosity and doesn't predict talent.
How the result changes with arm span
Holding every other input at the first worked example, this table changes only arm span. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Arm span | Ape index | Difference |
|---|---|---|
| 90 | 0.514 | -85 |
| 180 | 1.029 | 5 |
| 360 | 2.057 | 185 |
| 720 | 4.114 | 545 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Arm span: entering "0" shows "Arm span must be greater than 0." beside that field and no result.
- Height: entering "0" shows "Height must be greater than 0." beside that field and no result.
Choosing between the Ape Index Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Ponderal Index Calculator](/health/ponderal-index/) | weight and height | Ponderal index |
| [BMI Calculator](/health/bmi-calculator/) | units, weight and height | Your BMI |
| [Height Calculator](/health/height-calculator/) | convert | Height |
| [Body Fat Calculator (U.S. Navy)](/health/body-fat/) | sex, height and neck | Estimated body fat |
| [Ideal Weight Calculator](/health/ideal-weight-calculator/) | units, sex and height | Ideal weight (Devine) |
Background: body measurements and screening
Body-measurement ratios are screening tools, not diagnoses. BMI ignores body composition and fat distribution, and reviews find waist-to-hip and waist-to-height ratios are useful additions but not clearly better than BMI or waist circumference alone. Where the tape goes matters, so measure at the same sites each time.
Some sources quote a waist-to-hip ratio above 0.8 for women and 0.95 for men as a marker of increased metabolic risk; treat that as a screening flag, and talk to a clinician about what your own numbers mean.
Assumptions and limitations
- Same unit for both
- Not a diagnosis
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for arm span and height to confirm this.
Frequently asked questions
Is a higher ape index better?
It can help in climbing and swimming.
Does it change with age?
Height can shrink; span is stable.
What is a negative ape index?
A span shorter than height.
What does the Ape Index Calculator calculate?
Arm span compared with height. It returns Ape index and Difference.
What formula does the Ape Index Calculator use?
ape index = arm span ÷ height. A ratio above 1 means arm span exceeds height; use the same unit for both.
What do I need to enter in the ape Index Calculator?
You enter Arm span and Height.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Same unit for both.
What are the limits of this calculator?
Same unit for both. Not a diagnosis.
What is an example of a ape Index result?
With arm span 180 and height 175, the ape index is 1.029.
Where does the method come from?
The method follows: Common definition used on this page. No single authoritative standard defines it, so the exact formula is stated in the formula section above: arm span ÷ height.
Can I rely on this calculator for a decision?
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health. For this calculator in particular: Same unit for both.
Related calculators
- Ponderal Index Calculator — Weight relative to the cube of height.
- BMI Calculator — Find your Body Mass Index (BMI) and weight status.
- Height Calculator — Convert height between centimeters and feet-and-inches.
- Body Fat Calculator (U.S. Navy) — Estimate body fat percentage from tape measurements (U.S. Navy method).
- Ideal Weight Calculator — Ideal body weight by four published formulas (Devine, Robinson, Miller, Hamwi).
- Waist-to-Hip Ratio Calculator — Waist-to-hip ratio and WHO risk threshold.
- Shannon Diversity Index Calculator — Shannon–Wiener diversity index from species counts.
- Simpson's Diversity Index Calculator — Simpson's index of diversity from counts.
Sources
- Common definition used on this page. No single authoritative standard defines it, so the exact formula is stated in the formula section above: arm span ÷ height
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.