Question 1

How do I calculate arrow spine?

Accepted Answer

Start with your peak draw weight, then adjust: add about 5 lbs per inch of arrow over 28 in, 5 lbs per 25 grains of total front-end weight over 100 gr (point + insert + collar + weight system), 0-10 lbs for cam type (compound), and 5 lbs if you shoot with fingers. Look up that effective draw weight against the carbon spine chart. A 60 lb compound shooting a 29 in arrow with a 100 gr front-end and a medium cam lands on 70 lbs effective, which maps to spine 300.

Question 2

What is arrow spine?

Accepted Answer

Arrow spine is the stiffness rating of a carbon or aluminum shaft, measured per the ASTM F2031 / ATA standard: the arrow is supported 28 inches apart and a 1.94 lb weight is hung at the centre. The amount it deflects, in thousandths of an inch, is the spine. A spine 340 arrow deflects 0.340 inches. Lower number = stiffer arrow.

Question 3

What is the formula for arrow spine?

Accepted Answer

There is no single algebraic formula — spine is a chart lookup. The convention every manufacturer uses is effective draw weight = draw weight + arrow length adjustment + front-end weight adjustment + cam adjustment + release adjustment. Cross that number against a chart like Easton's or Victory's to read your spine group.

Question 4

What counts as 'front-end weight' — just the point?

Accepted Answer

No — front-end weight is the total grains everything at the tip adds up to: point or broadhead + insert + collar + any weight system (Gold Tip FACT, Easton HIT, etc.). A 100 gr field tip with a 50 gr insert and 25 gr Ballistic Collar is a 175 gr front-end, which weakens dynamic spine far more than the 100 gr point alone would suggest. Both Gold Tip's and Victory's official spine selectors ask for this combined weight, not just the point.

Question 5

How do I calculate arrow spine for a compound bow?

Accepted Answer

Use your bow's peak draw weight (not holding weight), the exact arrow length from nock throat to shaft end, and your total front-end weight (point + insert + collar + weight system). Add 5 lbs per inch over 28 in, 5 lbs per 25 gr over 100 gr front-end, plus 0-10 lbs for cam aggressiveness. If you shoot with fingers instead of a mechanical release, add another 5 lbs. Chart the final number.

Question 6

How do I calculate arrow spine for a recurve bow?

Accepted Answer

Use your actual draw weight at your actual draw length (not the bow's labelled AMO weight). Adjust 3 lbs per inch of arrow length versus 28 in, 3 lbs per 25 gr of front-end weight versus 100 gr, and add 5 lbs for finger release — recurve archers always shoot with a tab or glove. The calculator applies the finger-release adjustment automatically when you pick Recurve. Target recurves at 35-40 lbs typically land on spine 500-600.

Question 7

How do I calculate spine for a traditional / wood arrow?

Accepted Answer

Wood shafts are rated directly in pounds (e.g. 45-50 spine). Match the wood spine to your effective draw weight at draw, plus small adjustments for arrow length and front-end weight. As a worked example: a 40 lb longbow drawing 28 in with a 125 gr front-end lands at about 48 lbs effective (40 + 3 for the heavy point + 5 for finger release), so the calculator recommends a 45-50 lb wood spine. As a rule of thumb, pick a shaft spined within 5 lbs of your effective draw weight and go stiffer (heavier-spined) if in doubt.

Question 8

What spine arrow do I need for a 60 lb compound bow?

Accepted Answer

For a 60 lb compound shooting a 28 in arrow with a 100 gr front-end and a medium cam, spine 340 is the standard recommendation. Go to 300 if your arrow is 30 in or you shoot a 125 gr broadhead with a 25 gr insert (150 gr front-end total). Drop to 400 if you shoot a 27 in arrow with 75 gr front-end or a soft cam.

Question 9

What spine arrow do I need for a 70 lb compound bow?

Accepted Answer

A 70 lb compound with a 29 in arrow and a 100 gr front-end (medium cam, mechanical release) lands at about 80 lbs effective, pointing to spine 250. A 300 is the next-weaker safe option. Heavier front-ends or hard cams push you to 200. Never drop to 340 at 70 lbs with a long arrow — under-spined flight is where broadhead groups fall apart.

Question 10

What happens if my arrow spine is too weak?

Accepted Answer

An under-spined arrow flexes too much on release. You will see fishtailing, wide groups (especially past 30 yards), broadhead planing, and vertical / horizontal tears in paper-tune tests. In extreme cases the arrow can snap at launch, which is dangerous. Always go stiffer than the chart when in doubt.

Question 11

What happens if my arrow spine is too stiff?

Accepted Answer

An over-spined arrow does not flex enough and tends to plane in the same direction as the rest offset (right for right-hand shooters). You will see stiff-tear in paper tuning and groups drift horizontally at distance. It is more forgiving than under-spined, but you lose a bit of forgiveness on broadhead flight.

Question 12

Is arrow spine the same across Easton, Gold Tip, Victory, and Black Eagle?

Accepted Answer

Yes for lines that print a deflection number (300, 340, 400, 500, etc.) — they all use the ASTM F2031 method, so those numbers are directly comparable. Some brands sell buffered weight-band products instead (Carbon Express Maxima Triad is typically offered as 300/350/400 by listed spine, and some lines cover a draw-weight range rather than a specific deflection). For those buffered shafts, follow the manufacturer's chart rather than mapping by number. Easton Genesis and Jazz use an older 1820-class AMO deflection that is not directly equivalent to a modern 800 carbon spine.

Question 13

Does front-end weight change the spine I need?

Accepted Answer

Yes — heavier front-ends weaken dynamic spine (the arrow flexes more at release because there's more inertia at the tip). The rule of thumb is 5 lbs of effective draw weight per 25 grains over 100 gr on compound (3 lbs on recurve / traditional). Going from a 100 gr to 125 gr total front-end is roughly half a spine group. Jumping to a 175 gr single-bevel + insert combo can push you a full spine group stiffer.

Question 14

How does arrow length affect spine?

Accepted Answer

Longer arrows flex more under the same load, so they need stiffer shafts. On a compound, every inch over 28 in adds about 5 lbs of effective draw weight; every inch under subtracts 5 lbs. A 30 in arrow on a 60 lb bow needs spine 340 or 300, while a 27 in arrow on the same bow might work with spine 400.

Question 15

How do I verify my spine is right?

Accepted Answer

Paper-tune or bareshaft at 15-20 yards. Shoot three field-tipped bareshafts with three fletched arrows at the same target. If they group together (tight cluster, no tail kick in paper), your spine is correct. If the bareshafts group left of the fletched (right-hand shooter), you are over-spined; right of the fletched means under-spined. Adjust shaft length, front-end weight, or spine until they match.

Question 16

What is the difference between static spine and dynamic spine?

Accepted Answer

Static spine is the lab number printed on the shaft (deflection under 1.94 lb). Dynamic spine is how the arrow actually behaves at launch with your bow, nock, fletching, and front-end weight. The chart converts static spine into a dynamic-spine-appropriate pick. Paper-tuning confirms dynamic spine is right for your setup.

Factor	Adjustment
Peak draw weight	+60.0 lbs
Medium cam	+5.0 lbs
Effective draw weight	65.0 lbs

Effective Draw Weight	Carbon Spine	Typical Archer
≤ 29 lbs	800	Youth / very light target
30-39 lbs	600	Light target recurve
40-49 lbs	500	Olympic recurve / light compound
50-59 lbs	400	Target compound / medium hunt
60-69 lbs	340	Most whitetail hunters
70-79 lbs	300	Heavy hunting compound
80-89 lbs	250	Elk / big-game setup
≥ 90 lbs	200	Extreme high-poundage

Arrow Spine Calculator

Effective Draw Weight Breakdown

Brand-Spine Matches

How We Calculated It

What Is an Arrow Spine Calculator?

How Is Arrow Spine Calculated?

Spine Selection by Bow Type

Quick Spine Reference Chart

Tips for Getting Spine Right

Frequently Asked Questions

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