A bow draw weight calculator translates your bow's draw weight and arrow setup into real-world performance numbers — arrow speed, kinetic energy, momentum, and front-of-center percentage. These metrics determine whether your setup is adequate for your intended game and help you tune for the best balance of speed and penetration.
Bow & Arrow Specs
Broadhead or field point weight — used for FOC calculation
From manufacturer spec sheet — used to estimate real speed
Hunting Adequacy (KE)
KE thresholds are guidelines — shot placement and broadhead choice are equally important. Always verify local regulations.
FOC Reference
Kinetic Energy Requirements by Game
Industry guidelines — verify with your local regulations
| Game Animal | Min KE (ft-lbs) | Recommended KE | Notes |
|---|---|---|---|
| Small Game (rabbit, squirrel) | 15 | 25+ | Check local regs |
| Turkey | 25 | 35–50 | Sharp broadhead critical |
| Whitetail Deer | 40 | 50–65 | Most popular NA bowhunt |
| Black Bear | 50 | 65–80 | Dense hide and muscle |
| Elk / Moose | 65 | 80–100 | Heavy bones, shoulder shots |
| Large / Dangerous Game | 100 | 120+ | Guides may require more |
How to Use the Bow Draw Weight Calculator
Understanding your bow's real-world performance before season is the hallmark of a responsible bowhunter. This bow draw weight calculator translates your equipment specs into arrow speed, kinetic energy, momentum, and FOC — the four numbers that determine if your setup is ready for the field.
Step 1: Select bow type and enter draw weight
Choose your bow type — compound, recurve, or longbow. Compound bows use a let-off mechanism that stores more energy and have IBO speed ratings. Recurves and longbows use a simpler efficiency model. Enter your draw weight in pounds (or kg if metric mode is enabled). Most adult bowhunters use 50–70 lbs draw weight.
Step 2: Enter draw length and arrow specs
Draw length significantly affects arrow speed — every inch under 30" reduces speed by 10–15 fps. Enter your total arrow weight (the shaft weight alone, without the point) and the point weight separately. Point weight is used for the front-of-center calculation, which is critical for arrow flight stability and penetration performance.
Step 3: Enter your bow's IBO speed (compound only)
For compound bows, enter the manufacturer's IBO speed rating from the bow spec sheet. The calculator adjusts this for your actual draw weight, draw length, and arrow weight to give a real-world estimated speed. IBO ratings assume 70 lbs, 30" draw, and a 350-grain arrow — your real speed will differ.
Step 4: Check hunting adequacy
The hunting adequacy section shows whether your kinetic energy meets recommended thresholds for small game, turkey, deer, bear, elk, and large dangerous game. Green means adequate, amber means borderline, and red means insufficient for that game size. Always prioritize shot placement over raw numbers — a poorly placed arrow at 80 ft-lbs is less effective than a perfect shot at 45 ft-lbs.
Optimizing your setup
To increase kinetic energy, you can raise draw weight, increase draw length, or use a heavier arrow (counterintuitively, a heavier arrow retains more KE at hunting distances). For better penetration on large game, focus on momentum (mass × velocity) over raw KE — a heavy, slow arrow often penetrates better than a light, fast one. Target an FOC of 10–15% for balanced hunting performance.
FAQ
Is this bow draw weight calculator free?
Yes, completely free with no account required. All calculations run in your browser — no data is sent to a server.
How much kinetic energy do I need for deer hunting?
Most bowhunting organizations recommend a minimum of 40 ft-lbs of kinetic energy for whitetail deer. Many experienced hunters prefer 50–65 ft-lbs for reliable penetration. For elk and other large game, 65 ft-lbs or more is commonly recommended. Small game like rabbits and squirrels can be taken with as little as 15–25 ft-lbs.
What is FOC (Front of Center) and why does it matter?
FOC (Front of Center) is the percentage by which the balance point of your arrow is forward of its geometric center. Higher FOC improves arrow stability and penetration. Most bowhunters aim for 10–15% FOC. Some hunters pursuing large game use high-FOC setups (20%+) for maximum penetration. Olympic target archers typically use lower FOC (7–9%) for flatter trajectory.
What is IBO speed rating for compound bows?
IBO (International Bowhunter Organization) speed is a standardized rating measured at 70 lbs draw weight, 30-inch draw length, and a 350-grain arrow at sea level. Real-world arrow speed will differ based on your actual draw weight, draw length, and arrow weight. The calculator estimates your real-world speed using these adjustments.
How do I increase my arrow's kinetic energy?
KE = ½ × mass × velocity². To increase KE, you can: (1) increase draw weight — heavier bow = more force on the arrow; (2) use a heavier arrow — counterintuitively, a heavier arrow retains more KE at distance than a lighter one; (3) increase draw length — more stored energy; or (4) reduce arrow weight for higher velocity. The trade-off between speed and mass is at the heart of bowhunting arrow selection.
Does draw length affect arrow speed?
Yes significantly. Every inch of draw length shorter than 30 inches (the IBO standard) reduces arrow velocity by approximately 10–15 fps. A 27-inch draw will be about 30–45 fps slower than the same bow at 30 inches, all else equal. Every inch of additional draw length increases velocity by the same amount.