Reach Advantage Calculator

What is reach and why it matters:

Reach (or arm span) is measured fingertip to fingertip with arms extended horizontally. In combat sports, reach determines who can strike first from distance. A fighter with longer reach can land jabs and front kicks while staying outside their opponent’s effective range.

Reach vs. height ratio:

Most people have an arm span roughly equal to their height (a 1:1 ratio, called the “Vitruvian” proportion). Fighters with a positive ape index (reach greater than height) have a natural distance advantage.

Ape Index = Reach - Height

Reach advantage between two fighters:

Raw reach advantage = Fighter A reach - Fighter B reach

Effective advantage = Raw advantage × Stance modifier

Example calculation:

Fighter A: 188 cm tall, 198 cm reach (Orthodox) Fighter B: 183 cm tall, 185 cm reach (Orthodox)

• Raw advantage: 198 - 185 = 13 cm
• Effective advantage: 13 × 1.0 = 13 cm
• Fighter A ape index: 198 - 188 = +10 cm (long reach)
• Fighter B ape index: 185 - 183 = +2 cm (above average)

Note where +10 falls. The bands above are read as “up to and including”, so +10 cm is the top of long reach rather than the bottom of exceptional. It takes more than +10 to earn that last row.

Now switch Fighter B to southpaw. The raw 13 cm does not change, but the open stance modifier does: 13 × 0.85 = 11.0 cm effective. Same bodies, less of an edge, because in an open stance the lead hands are on the outside and the shorter fighter can step off the line instead of walking straight into the jab.

Tactical implications by advantage size:

• 0–5 cm: Minimal difference. Technique and timing matter more than reach.
• 5–10 cm: Noticeable advantage. Longer fighter can maintain distance with jabs.
• 10–15 cm: Significant. Shorter fighter must use head movement and angles to close distance.
• 15+ cm: Dominant. Shorter fighter typically needs wrestling or clinch work to negate reach.