A compound bow looks like it should work the same way a recurve does: draw the string, aim, let go. It doesn't. The whole reason a compound bow exists is a small mechanical trick at each limb tip that changes how much force you're actually holding at full draw. Once that trick makes sense, the rest of compound bow terminology, let-off, cam type, draw cycle, falls into place on its own.
Cams and cables, not just bent limbs
A traditional recurve or longbow works the way it looks like it works: bend the limbs, and the string pulls back against that bend the entire time F001. Whatever weight you feel at the start of the draw is close to what you still feel right before release, when the bow is at peak tension.
A compound bow adds cams, eccentric (not perfectly round) pulleys mounted at each limb tip, connected by a system of cables instead of relying on limb-bend alone F001. As you draw the string back, the cables route around those cams, and because the cams aren't round, the leverage they provide changes continuously through the draw instead of staying constant. Early in the draw, you're fighting close to the bow's full weight. Partway through, the resistance actually peaks. Then the cam "rolls over," and the leverage flips in your favor. By full draw, you're holding a fraction of the bow's peak weight, not all of it.
That drop has a name, and it's the single most important spec on a compound bow's spec sheet.
What "let-off" actually means
Let-off is the percentage difference between a compound bow's peak draw weight and the weight you're actually holding once you reach full draw. Manufacturers print it as a single number, like 80% or 75%.
Run the math on an 80% let-off, 60-pound bow: 80% of 60 pounds is 48 pounds, so 48 pounds is what gets "let off." That leaves 20% of 60 pounds still in your hands, which is 12 pounds. You pull through a peak of roughly 60 pounds partway through the draw, but the bow you're actually holding at full draw, aiming and waiting for the right moment, only asks you to support 12 pounds of tension.
Most modern hunting compound bows land somewhere in the 65% to 90% let-off range, and on many bows it's adjustable within the cam or module system rather than fixed at one number. A higher percentage means less weight held at full draw. A lower one means more.
Single-cam, dual-cam, and hybrid-cam: what the difference actually is
Not every compound bow routes its cables the same way, and the three common setups trade off differently between smoothness, speed, and how much upkeep they need.
A single-cam bow has one round idler wheel on one limb and one eccentric power cam doing the actual work on the other, driven by a single cable plus a control cable. There's only one cam shaping the draw cycle, so there's nothing for it to fall out of sync with. That's why single-cam bows have a reputation for holding their tune with less maintenance.
A dual-cam (or twin-cam) bow puts a matched eccentric cam on both limbs, with two cables crossing between them. Both limbs load and release energy together, which is generally why dual-cam bows tend to shoot a little faster for a given draw weight. The tradeoff: two independently-moving cams can drift out of time with each other, called cam lean, so a dual-cam bow needs its timing checked periodically to keep both cams rolling over together.
A hybrid-cam system, sometimes called cam-and-a-half, splits the difference. It uses two cams like a dual-cam setup, but one of them is a smaller control cam that manages timing through its own dedicated cable rather than acting as a full power cam. The goal is single-cam-style reliability without giving up as much of a dual-cam's speed.
None of the three is objectively better. They're different answers to the same tradeoff between raw speed, tuning simplicity, and shot-to-shot consistency, and which one matters more depends on how you'll actually use the bow.
Why let-off is what makes a compound bow shootable at full draw
Here's the part that actually affects your shot: holding 12 pounds is a completely different experience than holding 60. At a high let-off, you can settle your sight pin, wait out a moving target, and check your form, all while at full draw, without your arm shaking from fatigue. Try holding a recurve at 60 pounds of peak tension for more than a second or two and you'll feel exactly why that matters. Let-off doesn't make the bow easier to draw back. It makes the bow easier to hold once you're already there, which is where most of the actual aiming happens.
That's also why a compound bow's peak weight and its holding weight are two different numbers worth knowing before you buy one, not just the single "draw weight" figure printed on the box.
Where to go from here
Understanding the cam-and-cable system is step one. If you want the full breakdown of every part on the bow itself, cams, cables, riser, limbs, string, and where axle-to-axle length fits in, our compound bow parts guide walks through the whole thing piece by piece. And if you're still deciding whether a compound bow is even the right type of bow for you, our compound bow vs. recurve bow guide lays out the real tradeoffs between the two.
FAQ
Does a compound bow's let-off make it "cheat" compared to a recurve?
No. Let-off changes how much weight you hold at full draw, not how much energy the bow stores or delivers to the arrow. A compound bow still requires you to pull through its full peak weight to get to full draw in the first place. What let-off actually buys you is more time to aim steadily once you're there, which is a real, mechanical difference in how the two bow types are used, not a shortcut around the draw itself.
Can you change the let-off on a compound bow?
On many bows, yes, within a range set by the cam or module system, since let-off is a function of the cam's shape and timing rather than something bolted on separately. It's not infinitely adjustable on every bow. Whether and how much a specific model can be adjusted depends on that bow's own cam design, which is worth checking against the manufacturer's spec sheet before assuming a bow can be tuned to a different let-off than it ships with.
Is a higher let-off always better?
Not necessarily. A higher let-off means less weight held at full draw, which helps with steadiness and reduces fatigue, but some archers prefer a slightly lower let-off because it keeps a bit more tension in the shot and can feel more connected to the string during release. It's a real preference tradeoff between comfort and feel, not a spec where higher is automatically correct for every shooter.
Do you still need physical strength to shoot a compound bow?
Yes, for the pull itself. You have to draw through the bow's full peak weight to reach full draw, and that peak is close to (sometimes higher than) the bow's stated draw weight, before let-off ever reduces anything. Let-off only changes what happens after you're already at full draw. A compound bow with a high peak weight is not automatically easy to draw just because it has a high let-off.
Sources
- [F001]-[F010] General, well-established archery equipment mechanics (cam-and-cable systems, let-off, single/dual/hybrid-cam design) : not tied to a single live source; see
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