Bow Let-Off Calculator
Three calculations in one tool — find your holding weight from peak draw and let-off%, back-calculate your actual let-off from two scale readings, or find the peak weight you need to achieve a target holding weight. Compound bow only.
💡 Use a bow scale for all measurements. Draw to your actual anchor point — don't over-draw or under-draw. For compounds, watch the scale during the draw stroke to catch both peak and valley readings.
What compound bow let-off actually means
Let-off is the percentage by which a compound bow's cam system reduces the draw weight at full draw compared to peak draw weight. A 60 lb bow with 80% let-off reaches 60 lbs during the draw stroke, then drops to just 12 lbs in the valley — you hold only 20% of peak weight. This mechanical advantage is created by the eccentric cam (or cams) rotating through an over-centre position, similar to how a pulley system stores and releases mechanical energy.
The distinction between peak weight and holding weight matters enormously for compound archers. Peak weight is used for arrow spine selection, kinetic energy calculations, and hunting regulation compliance. Holding weight determines how comfortable the bow is to shoot — and how long you can hold at full draw before fatigue or movement affects your shot.
For peak draw weight calculations at your specific draw length, see the Draw Weight Calculator. This page focuses exclusively on the let-off relationship between peak weight and holding weight.
Let-off percentage comparison — 60 lb bow
The table below shows holding weight and remaining stored energy for a 60 lb compound bow at different let-off percentages. Note how dramatically holding weight changes with relatively small let-off changes.
| Let-off % | Holding weight (60 lb peak) | Holding weight (70 lb peak) | Typical use |
|---|---|---|---|
| 60% | 24.0 lbs | 28.0 lbs | Target archery (more feel at full draw) |
| 65% | 21.0 lbs | 24.5 lbs | Target / 3D — responsive shot feel |
| 70% | 18.0 lbs | 21.0 lbs | Versatile — target and light hunting |
| 75% | 15.0 lbs | 17.5 lbs | All-around hunting and target |
| 80% | 12.0 lbs | 14.0 lbs | Standard hunting — most common |
| 85% | 9.0 lbs | 10.5 lbs | Hunting — long hold times, tree stands |
| 90% | 6.0 lbs | 7.0 lbs | Maximum hold ease — mobility limitations |
Formula: Holding weight = Peak weight × (1 − let-off% ÷ 100)
High let-off vs. low let-off — which is better?
The right let-off depends on how you shoot. There is no universally better option — it is a genuine trade-off between comfort and feel.
Arguments for higher let-off (80–90%)
High let-off lets you hold at full draw for longer with less muscular effort. For bowhunters sitting in a tree stand waiting for a deer to step into position, the ability to hold 8–10 lbs rather than 14–18 lbs for 10–20 seconds can be the difference between a steady shot and a shaky one. High let-off is also beneficial for archers with shoulder injuries or limited upper-body strength who still want to shoot heavier draw weights.
Arguments for lower let-off (60–75%)
Lower let-off means you hold more weight at full draw, which gives more tactile feedback and a more responsive feel at the shot. Many target and 3D archers prefer 65–75% because it creates a crisper back-tension shot with less of the "mushy" feeling some archers associate with very high let-off cams. Lower let-off also keeps slightly more energy stored in the system, contributing marginally to efficiency — though modern high-performance cams largely close this gap.
The practical sweet spot
For most compound bowhunters, 80–85% let-off is the practical sweet spot. It reduces holding weight enough to allow stable 10–15 second holds in field conditions, while preserving enough feel to shoot cleanly. Most major bow manufacturers default to 80% let-off on their hunting cams, with 85% increasingly common on premium hunting bows. Shop compound bows at Amazon filtered by let-off spec.
How to measure your bow's actual let-off
🛒 Shop bow scales on Amazon — a peak-hold digital bow scale is the easiest tool for capturing both peak and valley readings in one draw.
Limb bolt adjustments — what changes and what doesn't
When you adjust your compound bow's limb bolts to raise or lower peak draw weight, the let-off percentage stays essentially the same. The cam geometry that creates let-off is fixed — it does not change when you wind the limbs in or out. What changes is only the peak weight and, as a result, the holding weight in proportion.
| Limb bolt position | Peak weight | Holding weight (80% let-off) | Holding weight (85% let-off) |
|---|---|---|---|
| Max (fully in) | 70 lbs | 14.0 lbs | 10.5 lbs |
| −5 lbs (≈2 turns out) | 65 lbs | 13.0 lbs | 9.75 lbs |
| −10 lbs (≈4 turns out) | 60 lbs | 12.0 lbs | 9.0 lbs |
| −15 lbs (≈6 turns out) | 55 lbs | 11.0 lbs | 8.25 lbs |
⚠️ Never back limb bolts out more than the manufacturer's maximum — typically 4–6 full turns out from fully seated. Limb bolt turns per pound varies by bow model. Use the Draw Weight Calculator to check your actual peak weight after adjusting.
Let-off and arrow selection — what you must use
Always use peak draw weight — not holding weight — for every arrow-related calculation. This is the most common mistake compound archers make when setting up a new bow. The arrow spine chart, kinetic energy formula, grains-per-pound calculation, and hunting regulation minimum weights all reference peak weight.
Holding weight is irrelevant for arrow selection because the arrow is launched at peak energy, not valley energy. The cam has already stored the full peak energy and will release it into the arrow regardless of how little you feel at full draw.
🎯 Arrow setup workflow using peak weight:
- Find your actual peak draw weight → Draw Weight Calculator
- Select arrow spine based on peak weight → Arrow Spine Calculator
- Check kinetic energy for hunting → Kinetic Energy Calculator
- Verify grains per pound ratio → Draw Weight Calculator (GPP section)
Tools for measuring let-off accurately
- Digital bow scales — Amazon (peak-hold models capture both peak and valley readings)
- Bow presses — Amazon (required for cam module changes)
- Draw boards — Amazon (precise draw weight measurement at any draw length)
Bow let-off FAQs
What is let-off on a compound bow?
Let-off is the percentage reduction in draw weight at full draw compared to peak draw weight. An 80% let-off bow that peaks at 60 lbs requires you to hold only 12 lbs at full draw. The cams create this reduction by rotating through an over-centre position as you reach the end of the draw stroke.
How do I calculate my holding weight?
Holding weight = peak draw weight × (1 − let-off% ÷ 100). Use the calculator above — enter your peak weight and select your let-off percentage for an instant result. For your actual peak weight at your draw length, use the Draw Weight Calculator first.
How do I find my bow's actual let-off percentage?
Measure peak weight (highest reading during draw) and holding weight (reading in the valley at full draw) with a bow scale, then enter both values in the "Find let-off %" tab above. The formula is: let-off% = (1 − holding ÷ peak) × 100.
Does higher let-off mean a worse bow?
No — it means a different bow suited to different uses. High let-off (85–90%) is better for hunting situations requiring long holds, or for archers with shoulder limitations. Lower let-off (65–75%) gives more feel at full draw and is preferred by many target and 3D archers. Most hunting bows use 80–85% as a practical balance.
Can I change my bow's let-off?
Let-off is set by the cam module design. Some bows offer alternative cam modules with different let-off percentages — switching requires a bow press and is a pro-shop job. Limb bolt adjustments change peak weight but do not change the let-off percentage.
Should I use holding weight or peak weight for arrow spine selection?
Always use peak weight. Arrow spine charts, kinetic energy formulas, and hunting regulation minimums all reference peak draw weight — not holding weight. The arrow is launched at peak stored energy, regardless of how light the holding weight feels. Using holding weight for spine selection will result in arrows that are too weak, causing poor flight and potential tuning problems.
What let-off is best for hunting?
Most bowhunters do well with 80–85% let-off. This range allows comfortable holds of 10–20 seconds in field conditions while preserving enough draw weight feel for a clean shot break. Some hunters prefer 85–90% for cold-weather hunting (heavier clothing reduces mobility) or for situations requiring very long holds. Lower let-off (65–75%) is uncommon in hunting setups but preferred by some traditional-leaning compound archers.