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Arrow Spine Calculator

Find the recommended arrow spine (stiffness) from your draw weight, arrow length, point weight and bow type.

Recommended spine
400
340–500
Effective draw weight: 50.0 lbs
SoftStiff
800700600500400340300

This is a starting-point estimate only. An arrow that is too soft (too weak) for your setup can break on the draw or at release and cause injury. Always confirm the spine you actually shoot against the maker's spine chart or with a pro shop.

Source: estimate based on major-maker spine charts (Easton, Gold Tip, Victory, etc.) and common archery tuning guidance.

What is the arrow spine calculator?

Arrow spine is a measure of how stiff an arrow shaft is. A lower spine number means a stiffer arrow (e.g. 300 = stiff) and a higher number means a softer, more flexible arrow (e.g. 800 = soft). This calculator estimates a recommended spine for your setup from your draw weight (lbs), arrow length (inches), point weight (grains), bow type and release style. The wrong spine makes arrows fly poorly and lose accuracy, and an arrow that is far too soft can become a safety hazard.

How to use it

1. Pick your bow type (compound, recurve or longbow). 2. Enter your draw weight (lbs), arrow length (inches) and point weight (grains). 3. Choose your release type (finger or mechanical). 4. Read the recommended spine center value and range, the effective draw weight, and where it falls on the soft-to-stiff scale.

How it is calculated

We first work out an effective draw weight. Starting from a 28-inch arrow with a 100-grain point, every extra inch of arrow length adds about +5 lbs and every extra 25 grains of point weight adds about +4 lbs of "needs a stiffer arrow". Recurve and longbow setups, and finger releases, are adjusted toward a softer arrow because of archer's paradox (the arrow flexing around the bow at the shot). This effective draw weight is then matched to a band that mirrors a maker's spine chart to give a recommended spine range and a representative center value.

Reading the result

The large number is the representative recommended spine; the range below it is the practical tuning window. Treat it as a starting point: final tuning still needs real shooting tests such as bare-shaft or paper tuning. Avoid an arrow that is too soft (a number that is too high), and when in doubt start from the stiffer (lower-number) end of the range.

FAQ

What is arrow spine? ▾

Spine is a measure of how stiff an arrow shaft is. By convention a lower spine number is stiffer and a higher number is softer. If the spine does not match your draw weight and bow, the arrow will not fly cleanly or group well.

What is the difference between dynamic and static spine? ▾

Static spine is the raw material stiffness, measured as how far the shaft deflects under a fixed load between fixed supports. Dynamic spine is how the arrow actually behaves at the shot, once point weight, arrow length, nock and fletching, and the bow's output are included. This calculator applies those corrections to estimate something close to dynamic spine.

How do I measure arrow length? ▾

Arrow length is usually measured from the bottom of the nock groove to the end of the shaft (where the point seats). It is normally left a little longer than your draw length. A longer arrow behaves softer, so it needs a stiffer spine. Follow your shaft maker's exact definition for best results.

How does point weight affect spine? ▾

A heavier point gives the front of the arrow more inertia, so the shaft flexes more at the shot and behaves softer. That means a heavier point generally calls for a stiffer spine to compensate.

Why does the recommendation change with bow type? ▾

Compound bows shoot the arrow with cams and a mechanical release, so the arrow flexes less and a relatively stiffer spine suits. Recurve and longbow setups, especially with a finger release, see much more archer's paradox and need a softer arrow.

This calculator provides general estimates for informational purposes only and is not medical advice. Consult a qualified healthcare professional before making decisions about your health.