Arrow weight calculator

GPI, grains, and GPP describe different things

GPI means grains per inch. It describes shaft mass along its length, so a shaft listed at 8 GPI contributes 8 grains for each inch of shaft material. Use the GPI for the exact shaft model and spine size you plan to buy. Different sizes in the same product family may have different values.

Grains describe mass. The arrow grain guide explains the unit used on point and shaft labels. A point labeled 100 grains contributes that much to the build before you add the shaft and other parts. Make sure a digital scale is displaying grains rather than grams before comparing its reading with the calculator.

GPP means grains per pound of bow draw weight. It relates the finished arrow mass to the bow. For a compound, use peak draw weight rather than the reduced holding weight after let-off. Changing the bow's draw weight changes GPP even when you keep the same arrows.

Add the components without counting anything twice

Total weight = shaft GPI x shaft length + point + insert + nock + fletching x count + wrap. All component weights in this formula are in grains, and shaft length is in inches. Enter the weight of one vane or feather before multiplying by the number fitted.

• Measure the bare shaft material for the GPI calculation. A nock-throat-to-shaft-end measurement can include some nock length, which would overstate the shaft contribution.
• Use the finished point weight, including any point sections that will remain installed. For a screw-in system, count the insert separately unless the listed assembly weight already includes it.
• Include nock pins, bushings, collars, or outserts where your arrow uses them. Add their mass to the appropriate component subtotal if there is no separate input.
• Check whether a fletching weight describes one vane, one feather, or a complete set. Count the wrap once per arrow.
• Leave absent components at zero. An arrow with a glue-in point may not use a separate screw-in insert.

Small parts are easy to miss on a worksheet. Lay out one complete set before assembly and compare it with the entries. Adhesive also adds mass, so the component calculation remains an estimate until you weigh the finished arrow.

Worked build: 398 grains at 60 pounds

This example starts with a 29 in bare shaft rated at 8 GPI. The table adds a point, insert, and nock, then three vanes and a wrap. Use the actual specifications of your own compatible parts in place of these sample weights.

GPP = total arrow weight / peak draw weight. On a compound measured at 60 lb peak weight, this example gives 398 / 60 = 6.63 GPP after rounding. If the same arrow is used on a 70 lb bow, it gives 398 / 70 = 5.69 GPP. The arrow has not changed; the bow input has.

For a recurve, use the draw weight measured at your actual draw length when evaluating the arrow-to-bow weight ratio, and follow the manufacturer's instructions. A limb marking at a reference draw length can differ from the weight you actually draw.

Use the bow manual to check minimum arrow weight

The IBO minimum is 5 grains per pound. Many compound manufacturers also specify a minimum around 5 GPP, but your bow's stated minimum governs the setup. A calculator result above 5 GPP does not override a higher requirement, a model-specific instruction, or an incompatible shaft selection.

If a bow manual specifies 5 GPP at 60 lb peak draw weight, the arithmetic gives a 300 grain minimum complete arrow. That is an example of applying a stated limit, not a recommendation to build at the lightest permitted weight. Never shoot below the manufacturer's minimum or dry fire the bow.

The calculator does not verify shaft stiffness, point compatibility, or arrow condition. Check those separately before shooting. An arrow can meet a weight requirement and still be unsuitable because it is too short, damaged, or incorrectly matched to the bow.

What adding weight changes on the range

With the same bow settings, a heavier arrow generally leaves the bow more slowly. It also changes how the bow transfers its stored energy, and it can change the sound of the shot. Noise depends on the whole setup, so a grain total alone cannot predict how quiet a bow will be.

Use the arrow speed calculator to estimate the effect of a planned mass change, then verify the finished build with a chronograph. For example, replacing a 100 grain point with a 125 grain point adds 25 grains if all other parts stay the same. Changing the insert at the same time requires adding its difference too.

Where you add weight also matters. Heavier front components tend to move the balance forward, while a heavier nock or rear wrap moves it rearward. The FOC calculator measures that balance after assembly. Two arrows with equal total mass can have different balance points.

Check the finished set on a scale

Zero the scale and weigh complete arrows in their shooting configuration. Keep the arrows still and clear of anything that could support part of their weight. Record each result rather than weighing one arrow and assuming every other arrow matches it.

If an arrow differs noticeably, inspect its parts before trying to correct the mass. A different nock, missing wrap, wrong point, or different fletching count may explain the reading. Check the worksheet against the physical arrow, then save the measured total as the value for future speed or energy calculations.

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