How to Choose the Right Arrow Spine for Your Bow Setup

Spine is the single most important spec on a custom arrow order. Get it right and your arrows recover fast, group tight, and fly broadheads like field points. Get it wrong and no amount of expensive components will save the build. The good news: choosing spine is a solvable problem with three inputs and a chart. Here's how it works.

What Is Arrow Spine?

Spine is a measure of how much an arrow shaft resists bending. The industry standard test supports a shaft on two points 28 inches apart, hangs a 1.94 lb weight from the middle, and measures how far the shaft sags in thousandths of an inch. That deflection isthe spine number:

The counterintuitive part: a lower number means a stiffer arrow. A 300 spine bends less than a 500 spine. Once that clicks, spine charts stop being confusing.

Static vs. dynamic spine

The number printed on the shaft is static spine — how the bare shaft measures on the test bench. Dynamic spineis how the finished arrow actually flexes when your bow slams it forward at launch. Static spine is fixed; dynamic spine changes with your draw weight, arrow length, point weight, and even your bow's cam design. Selecting spine is really about matching dynamic spine to your bow, using static spine as the starting point.

The Three Inputs That Decide Your Spine

1. Draw weight

More poundage bends the arrow harder at the shot, so higher draw weight needs a stiffer spine. This is the first axis on every manufacturer's spine chart.

2. Arrow length

A longer arrow is easier to bend — the same shaft acts weakeras it gets longer. Cutting an arrow shorter stiffens its dynamic spine. This is the second axis on the chart, and it's why you should decide your finished arrow length before picking spine.

3. Point weight

Weight on the front of the arrow makes it flex more during acceleration — a heavier point makes the arrow act weaker. Most spine charts assume a 100gr point. A useful rule of thumb: every 25gr of additional point weight acts roughly like adding 5 lbs of draw weight. Planning a 150gr or 175gr head for a high-FOC build? Shop the chart as if your bow were pulling 10–15 lbs more.

A Broad Starting Point

Always confirm against the chart for your specific shaft, but for a modern compound at typical hunting lengths (27–29") with a 100gr point, most shooters land here:

• 40–50 lbs — 500 spine
• 50–60 lbs — 400 spine
• 60–70 lbs — 340/350 spine
• 70+ lbs — 300 spine or stiffer

Symptoms of the Wrong Spine

Too weak (the more common and more punishing mistake):

• Broadheads impact consistently away from field points and "plane" in flight
• Groups fall apart as draw weight or point weight goes up
• Erratic arrow flight that gets worse at distance

Too stiff:

• Generally more forgiving, but can show stubborn tune issues that small rest adjustments won't fix
• Often costs a little arrow speed from the extra shaft weight of stiff, heavy shafts

If your arrows are the right spine and still misbehave, check nock fit and broadhead alignment before blaming the shaft — both cause "spine-looking" symptoms.

Spine and FOC: Choose Them Together

Because point weight affects both numbers, spine and FOC have to be selected as a pair. Build the arrow on paper first — length, point, insert, vanes, nock — then pick the spine for that finished configuration. Our FOC guide covers the other half of that equation, and the free FOC Calculator lets you test component combinations in seconds.

Skip the Guesswork

The Arrow Ops 3D builderlists every available spine for the shaft you pick and shows total arrow weight, GPI, and live FOC as you configure. Set your arrow length, pick your point weight, and sanity-check the result against your bow's draw weight using the brackets above. Still torn between two spines? Reach outwith your draw weight, draw length, and intended point weight — we'd rather help you get it right before the carbon gets cut.