An arrow has to match your bow. Spine has to suit your draw weight and setup, and an arrow that's too light can damage the bow. This page walks through spine, weight, front-of-center (FOC) and cut length, mostly from Easton's own guides and bow makers' manuals.
My arrows are Black Eagle, custom cut to my draw length. I don't know my draw length number. A pro fitted my bow, and I think everyone should go to a trusted bow technician. For draw weight and kinetic energy, see draw weight for deer. For the rest of the setup, see the bowhunting setup guide by budget.
Spine: how stiff the arrow is
Easton defines spine as how far a 29-inch shaft bends with a 1.94 lb (880 gram) weight hung from its center, supported at points 28 inches apart. The bend in inches times 1,000 is the spine number. So a 500 spine bends half an inch, and a lower number means a stiffer arrow.
Reading Easton's chart
Easton's hunting chart picks a spine range from your bow weight and arrow cut length. It assumes a bow rated 301 to 340 fps ATA, a 100-grain screw-in point and a release aid. Adjust your bow weight on the chart if your setup differs:
| If your setup has | Adjust bow weight |
|---|---|
| Finger release | Add 5 lb |
| Bow rated up to 300 fps | Subtract 5 lb |
| Bow rated 341 to 350 fps | Add 5 lb |
| Bow rated 351 fps or more | Add 10 lb |
| Point over 100 grains | Add 3 lb per 25 grains over |
| Point under 100 grains | Subtract 3 lb per 25 grains under |
Easton says the main reason hunters pick the wrong arrow from the chart is guessing draw weight and draw length instead of measuring. A bow scale like the Last Chance Archery Bow Scale 3.0 measures peak weight. Last Chance says to nock an arrow first in case of a dry fire.
Arrow weight: the minimum
Mathews and Hoyt both say never to shoot an arrow lighter than 5 grains per pound of draw weight. At 70 pounds, that's 350 grains. Mathews says an underweight arrow acts like a dry fire and can damage the bow and hurt you, and Hoyt's warranty is void if you shoot one.
How to figure total weight
Easton rates shafts in grains per inch (GPI), and that number doesn't include the point, insert, nock or fletching. Multiply GPI by your cut length, then add the components. One grain is 1/7,000 of a pound.
Mathews notes IBO speed ratings use a 350-grain arrow at 70 pounds and a 30-inch draw, and a heavier arrow lowers your speed. For what that means at the target, see draw weight for deer.
FOC: front-of-center
FOC is the share of the arrow's weight in its front half. Easton recommends 10 to 15 percent FOC for hunting setups and says FOC matters for accuracy, especially at long range. Heavier points or inserts raise FOC, and per Easton's chart, they also change the spine you need.
Cut length
Easton measures arrow length from the bottom of the nock groove to the end of the shaft, not including the point or insert. Your cut length depends on your draw length and setup, so this is a good job for a bow technician. Easton also notes that changing arrow length changes how stiff the arrow acts when shot.
Other good options
- Easton's online selector and app run the chart with your numbers.
- An authorized retailer. Mathews lists correct arrow selection among the services its retailers handle.
Questions hunters ask
What spine do I need? Use the maker's chart with your measured draw weight and cut length, then adjust for your setup.
How heavy should my arrow be? At least 5 grains per pound of draw weight, per Mathews and Hoyt. Above that is a speed vs weight trade.
What FOC should I aim for? Easton recommends 10 to 15 percent for hunting.
Sources
- Easton, "Arrow Shaft Selection: Hunting" chart: https://eastonarchery.com/wp-content/uploads/2023/08/301055-A-Arrow-Shaft-Selection-Hunting.pdf
- Easton, Target & Hunting Arrow Selector: https://eastonarchery.com/selector/
- Easton, FAQs: https://eastonarchery.com/faqs/
- Mathews, FAQ: https://mathewsinc.com/pages/faq
- Mathews owner's manual (2017): https://issuu.com/mathews-inc/docs/2017_mathewsom/8
- Mathews, Mission Archery FAQ (IBO rating conditions): https://mathewsinc.com/pages/mission-archery-faq
- Hoyt, Limited Lifetime Warranty: https://s3.hoyt.com/uploads/2019/5bdb215acfff6060323583.pdf
- Last Chance Archery, Bow Scale 3.0 instructions: https://lastchancearchery.com/product/lca-bow-scale-3-0-hanging-model/