Tool · Arrow spine

Arrow spine chart & calculator

The spine your compound bow needs, from your draw weight, arrow length, point weight and bow speed, with the full chart behind it.

Bow

Peak draw weight?

70lb

IBO speed rating?

335fps

Arrow

Arrow length?

28.5in

Point type?

Point weight?

100gr

Insert weight?

15gr

How spine works and how to pick it: the arrow setup guide →FOC, speed and kinetic energy for the same arrow in the Arrow Lab →

About this tool

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Spine is how stiff an arrow shaft is. The number is how far the shaft bends, in thousandths of an inch, when a 1.94-pound weight hangs from its middle on a 28-inch span: a 300 bends 0.300 inches, a 400 bends 0.400. A lower number is a stiffer shaft.

To read the chart, start from your bow's peak draw weight and adjust it the way Easton's chart notes say: add 3 lb for every 25 grains of tip weight (point plus insert) over 100, add 5 lb for a bow rated 341–359 fps IBO or 10 lb at 360 and up, and take 5 lb off at 300 or less. Then find that weight's row and your arrow length's column. This calculator also adds 5 lb for fixed-blade broadheads, which is common tuning advice rather than part of Easton's notes.

Worked example: a 70-lb bow rated 335 fps, a 28.5-inch arrow, a 100-grain point and a 15-grain insert. The 115-grain tip adds 1.8 lb, for 71.8 lb. That row and the 29-inch column read 340 / 300, so a 340 spine, with 300 as the stiffer option.

Each cell gives two sizes. The calculator picks the weaker one for field points and mechanical broadheads, and the stiffer one for fixed blades on heavy bows, as most pro shops would.

FAQ

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

With a 27- to 29-inch arrow, a 100-grain point and a bow rated 301–340 fps, Easton's chart gives 340, with 300 as the stiffer option. At 30 inches it moves to 300. Heavier points or a faster bow push you stiffer.

What does the spine number mean?

It's how far the shaft bends, in thousandths of an inch, under a 1.94-pound weight hung from its middle on a 28-inch span. A 340 bends 0.340 inches; lower numbers are stiffer.

Does point weight change the spine I need?

Yes. A heavier point makes the arrow act weaker, so Easton adds 3 lb to your draw weight for every 25 grains of tip weight over 100 before you read the chart.

Should I pick the weaker or the stiffer size?

The weaker size suits field points and mechanical heads in the lower part of the weight bracket. Go stiffer for fixed-blade broadheads, heavy points, fast bows, or when your calculated weight is near the top of its row.

Are all brands' spine charts the same?

No. Easton, Gold Tip, Victory and Black Eagle each publish their own, and they usually agree within one size. Check the chart for the shaft you're buying.

Reference

For overspine and underspine, and how spine trades against point weight and FOC, see the arrow setup guide.

READ THE GUIDE →

Recommended spine

340

One size either way: 300 stiffer, 400 weaker.

How we got there

Calculated bow weight · 71.8 lb

Peak draw weight70 lb
Tip 115 gr (point + insert)+1.8 lb

Spine ruler · industry shafts

340

200

250

300

340

400

500

600

700

← Stiffer (lower number)Weaker (higher number) →

Arrow spine chart

Peak draw weight (rows) by arrow length in inches (columns), for a bow rated 301–340 fps IBO, shot with a release and a 100-grain tip. Each cell gives two sizes, weaker / stiffer.

Draw weight	23"	24"	25"	26"	27"	28"	29"	30"	31"	32"	33"	34"
up to 26 lb	—	—	—	700/600	700/600	600/500	600/500	500/400	500/400	500/400	400/340	400/340
27–31 lb	—	—	700/600	700/600	600/500	600/500	500/400	500/400	500/400	400/340	400/340	400/340
32–36 lb	—	700/600	700/600	600/500	600/500	500/400	500/400	500/400	400/340	400/340	400/340	340/300
37–41 lb	700/600	700/600	600/500	600/500	500/400	500/400	500/400	400/340	400/340	400/340	340/300	340/300
42–46 lb	700/600	600/500	600/500	500/400	500/400	500/400	400/340	400/340	400/340	340/300	340/300	340/300
47–51 lb	600/500	600/500	500/400	500/400	500/400	400/340	400/340	400/340	340/300	340/300	340/300	300/250
52–56 lb	600/500	500/400	500/400	500/400	400/340	400/340	400/340	340/300	340/300	340/300	300/250	300/250
57–61 lb	500/400	500/400	500/400	400/340	400/340	400/340	340/300	340/300	340/300	300/250	300/250	300/250
62–66 lb	500/400	500/400	400/340	400/340	400/340	340/300	340/300	340/300	300/250	300/250	300/250	250/200
67–72 lb	500/400	400/340	400/340	400/340	340/300	340/300	340/300	300/250	300/250	300/250	250/200	250/200
73–78 lb	400/340	400/340	400/340	340/300	340/300	340/300	300/250	300/250	300/250	250/200	250/200	250/200
79–84 lb	400/340	400/340	340/300	340/300	340/300	300/250	300/250	300/250	250/200	250/200	250/200	200/150
85–90 lb	400/340	340/300	340/300	340/300	300/250	300/250	300/250	250/200	250/200	250/200	200/150	200/150

Your setup reads from the highlighted cell: 71.8 lb calculated, 29-inch column.

Based on Easton's 2024 hunting arrow size chart. Other makers' charts usually land within one size of it; check the chart for the shaft you buy.