Arrow Speed Calculator

Updated Sep 2026 Used 0 times

Choose the speed sourceMeasured speed is more reliable than a setup estimate.

Speed source

Use a chronograph result when available; it removes the largest uncertainty.

Measured arrow speed

Enter launch speed measured by a chronograph for this exact bow and arrow.

Published IBO speed

Enter the manufacturer IBO speed baseline.

Draw length

IBO estimates use a transparent 10 fps per inch adjustment from the common 30-inch baseline.

String accessory speed loss

Enter a measured or manufacturer-supported loss for peep, loop, silencers, and other string weight.

Enter arrow and bow weightFinished arrow weight drives energy, momentum, and grains per pound.

Finished arrow weight

Use finished arrow weight including point, insert, shaft, nock, and fletching.

Peak draw weight

Used to calculate grains per pound. Follow the bow and arrow manufacturer minimums.

Guest calculations stay on this device. Signed-in results sync privately.

Your result

Arrow speed and impact metrics

Enter your values, then calculate to see a verified result.

Inputs usedReview the information used for this result.

Full calculation and sourcesOpen Full calculation and sources to see every estimate and physics conversion.

Versioned calculationFormula v1.0.1

Measured mode first

Use chronograph FPS when available and avoid unnecessary modelling.

Estimate inputs stay visible

Draw-length, arrow-weight, and accessory adjustments are not hidden.

Physics plus safety context

Energy, momentum, and grains per pound are shown without turning them into a species recommendation.

Choose measured or estimatedChronograph data is strongest.280 fps measured

Enter finished arrow weightInclude every installed component.425 grains

Review all four metricsRead FPS with energy, momentum, and GPP.Do not judge the setup by FPS alone

Interpretation

Kinetic energy changes with the square of speed.

Momentum changes linearly with mass and speed.

Spine, tune, broadhead flight, distance, and manufacturer limits remain separate checks.

Use this result

Audit the speed modelCheck the measured or IBO branch and the energy and momentum equations.Check setup limitsKeep arrow weight, draw weight, tune, and chronograph limitations with the result.

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Public verification recordFormula v1.0.1

Review scope: Measured Or IBO-estimated Launch Speed Plus Kinetic Energy, Momentum, And Grains-per-pound Calculations.
Review team: CalculatorGeek Algorithmic Team
Verified: 2026-09-26
Next source review: 2027-09-26
Automated fixtures: 6 cases

Review method

Unit constants were derived independently, measured and IBO branches were recomputed, gram/kilogram normalization was checked, and unsafe or invalid weight boundaries were exercised.

Known limitations

IBO mode is a heuristic estimate; cam design, draw-force curve, tune, string condition, release, and chronograph placement affect actual speed.
The physics outputs describe launch conditions and do not predict downrange velocity, penetration, trajectory, or broadhead performance.
Grains per pound does not replace the manufacturer arrow-spine chart or minimum-weight requirement.
No hunting species or legal suitability is inferred from kinetic energy or momentum.

Primary sources

Latest update

2026-09-26 · Restored unified Use this result cards, four related-calculator cards, and authored contextual links with valid root-relative destinations.

Published calculation checks

Case	Inputs	Expected result
Measured 280 fps 425 grain arrow	mode=measured, measured_speed=280 fps, ibo_speed=320 fps, draw_length=29 in, accessory_loss=5 fps, arrow_weight=425 grains, draw_weight=70 lb	arrow_speed=280, grains_per_pound=6.071428571428571, kinetic_energy=74.0049751243781
IBO estimate with heavier arrow	mode=ibo, measured_speed=280 fps, ibo_speed=320 fps, draw_length=29 in, accessory_loss=5 fps, arrow_weight=400 grains, draw_weight=65 lb	arrow_speed=288.3333333333333, grains_per_pound=6.153846153846154
IBO baseline	mode=ibo, measured_speed=300 fps, ibo_speed=340 fps, draw_length=30 in, accessory_loss=0 fps, arrow_weight=350 grains, draw_weight=70 lb	arrow_speed=340, grains_per_pound=5, classification=light-arrow
Metric weight normalization	mode=measured, measured_speed=250 fps, ibo_speed=320 fps, draw_length=73.66 cm, accessory_loss=5 fps, arrow_weight=25.9196 grams, draw_weight=29.4835 kg	arrow_speed=250

On this page

Direct answer

The arrow speed calculator uses either a chronograph speed or a transparent IBO-based estimate, then computes kinetic energy, momentum, and arrow grains per pound.

Measured chronograph speed is the stronger input. The IBO estimate applies published baseline conditions and simple setup adjustments, so it is labeled as an estimate rather than a promise of actual launch speed.

For propulsion and speed-through-water estimates, use the Boat Speed Calculator. For another measurement-led equipment fit, use the Golf Club Length Calculator.

How to use the calculator

Choose measured chronograph speed or IBO estimate mode.
Enter the exact finished arrow weight and peak draw weight.
For IBO mode, enter published IBO speed, draw length, and accessory loss.
Review speed, kinetic energy, momentum, grains per pound, and the manufacturer warning.

Inputs, outputs, and result meaning

Inputs

Speed source: Use a chronograph result when available; it removes the largest uncertainty.
Measured arrow speed: Enter launch speed measured by a chronograph for this exact bow and arrow.
Published IBO speed: Enter the manufacturer IBO speed baseline.
Draw length: IBO estimates use a transparent 10 fps per inch adjustment from the common 30-inch baseline.
String accessory speed loss: Enter a measured or manufacturer-supported loss for peep, loop, silencers, and other string weight.
Finished arrow weight: Use finished arrow weight including point, insert, shaft, nock, and fletching.
Peak draw weight: Used to calculate grains per pound. Follow the bow and arrow manufacturer minimums.

Outputs

Arrow speed: the primary answer for the selected calculation.
Kinetic energy: a supporting value used to interpret or cross-check the result.
Momentum: a supporting value used to interpret or cross-check the result.
Arrow weight per draw pound: a supporting value used to interpret or cross-check the result.
Weight adjustment from 350 gr: a supporting value used to interpret or cross-check the result.

Formula and methodology

IBO estimate: IBO speed + 10 x (draw length - 30) - (arrow weight - 350) / 3 - entered accessory loss.

Kinetic energy: arrow weight in grains x speed squared / 450,240.

Momentum: arrow weight in grains x speed / 225,218.

Grains per pound: finished arrow weight / peak draw weight.

The weight adjustment follows manufacturer guidance as a general estimate. The 10 fps per inch draw-length rule is a visible heuristic and is not a replacement for chronograph testing.

Worked examples

Measured setup

A 425-grain arrow measured at 280 fps has about 74.00 ft-lb of kinetic energy. At 70 lb draw weight it is about 6.07 grains per pound.

IBO estimate

Start with 320 fps, subtract 10 fps for a 29-inch draw, about 16.67 fps for a 400-grain arrow, and 5 fps of entered accessory loss. Estimated speed is about 288.3 fps.

Interpretation and limitations

IBO mode is a heuristic estimate; cam design, draw-force curve, tune, string condition, release, and chronograph placement affect actual speed.
The physics outputs describe launch conditions and do not predict downrange velocity, penetration, trajectory, or broadhead performance.
Grains per pound does not replace the manufacturer arrow-spine chart or minimum-weight requirement.
No hunting species or legal suitability is inferred from kinetic energy or momentum.

Frequently asked questions

Is measured FPS better than an IBO estimate?

Yes. Chronograph speed from the exact setup removes most of the model uncertainty.

How is arrow kinetic energy calculated?

Multiply arrow weight in grains by speed squared, then divide by 450,240 to get foot-pounds.

How is arrow momentum calculated?

Multiply arrow weight in grains by speed in feet per second, then divide by about 225,218 to get slug-feet per second.

Why does a heavier arrow lower the speed estimate?

The documented estimate subtracts about 1 fps for each 3 grains above the common 350-grain IBO baseline. Actual behavior is bow-specific.

Is 5 grains per pound always safe?

It is a common minimum context, but the exact bow and arrow manufacturer instructions control.

Sources and transparency

Sources establish the governing definition, measurement context, or documented estimate. CalculatorGeek independently recomputed the public fixtures on 2026-09-26. An estimate remains an estimate even when the arithmetic is exact.