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Sit-and-Reach Flexibility Calculator

See how your sit-and-reach distance compares with adult norms.

How it is calculated

The tool assumes adult sit-and-reach scores follow a bell curve centred on 30 cm with a standard deviation of 7.5 cm. It turns your reach into a z-score, z = (reach − 30) / 7.5, and reads the percentile from the normal distribution (using an approximation of the error function). Reach is in centimetres, exactly as read on the box scale, and the output is a percentile with two decimals. The same average is applied to everyone: there is no age or sex input. Values far below the average approach 0% and values far above approach 100%, and a negative reading is accepted. The scale on your box matters, because the tool takes the number as it is.

Worked example

You reach 38 cm on the box scale. z = (38 − 30) / 7.5 = 1.067. The normal curve places a z-score of 1.067 a little below the 86th percentile. Result: 85.69%, meaning 38 cm beats roughly 86% of the assumed reference group. For comparison, a reach of 30 cm gives exactly 50.00%.

Try this example →

Common mistakes

  • Entering the distance past your toes instead of the reading on the box scale. Boxes often put the toe line at a mark such as 15 or 23 cm, and the tool expects the raw box reading, so check which one your box uses.
  • Entering inches or millimetres. The field is in centimetres.
  • Taking the best of many bouncing or jerking attempts. A slow, steady reach with knees straight and the hold shown is the figure to enter.
  • Testing cold. The result will usually be lower than after a short warm-up, so test under the same conditions each time.
  • Reading the percentile as a score out of 100. 85.69% means you rank above about 86% of the reference group, not that you reached 86% of a maximum.

About this calculator

The sit-and-reach test measures hamstring and lower-back flexibility by having you sit with legs extended and reach forward along a measured box or ruler as far as possible, and the resulting distance is compared against normative percentile tables built from large population samples, typically broken down by age and sex since flexibility naturally varies across both.

Physical education teachers, personal trainers and fitness assessors use this test as part of standard fitness batteries (such as the FitnessGram or YMCA protocols) because it requires almost no equipment and gives an easily repeatable measure of flexibility, and expressing a raw reach distance as a percentile makes it meaningful by showing where that result sits relative to other adults rather than as an isolated number.

This calculator takes your sit-and-reach distance in centimeters and returns your estimated flexibility percentile. It compares you with a single adult reference (average 30 cm, standard deviation 7.5 cm) and does not adjust for age or sex.

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