Draw Length Calculator

What this draw length calculator answers

Draw length is the distance the string travels from rest to your anchor, and every bow, arrow and release aid is sized around it. You cannot read it off a wall with a tape measure, because the number depends on how you stand, where you anchor and how your shoulders sit at full draw. What you can measure at home is your wingspan, the distance from fingertip to fingertip with both arms out level. Wingspan tracks draw length closely enough to put you in the right size range before any money changes hands.

Type your wingspan in inches or centimeters, pick one of the two standard formulas, and the calculator returns an estimated draw length rounded to the half inch, the true draw and AMO numbers a shop works with, an arrow length range, and the draw weight a bow rated at 28 inches pulls at your length. If you already have a measured nock to grip pivot distance, enter it in the second box and every row switches to that measured number instead of the estimate.

The two wingspan formulas and where they cross

Two rules of thumb show up in hunter education worksheets and pro shop fitting guides. The first divides wingspan by 2.5. The second subtracts 15 inches and divides by 2. They return the same answer at exactly one wingspan, 75 inches, where both give 30.0 inches of draw. Below 75 inches the divide by 2.5 rule reads higher; above it, the subtract 15 rule does.

For most adults the spread stays under an inch, which is inside the error of the measurement itself, so treat the two answers as one range rather than a contradiction. The divide by 2.5 version is the one most worksheets print and the one a shop expects to hear. The calculator shows the other formula beside your pick, so a 70 inch wingspan reads 28.0 inches on the first rule and 27.5 on the second, and either number is a sane place to start.

True draw length and AMO draw length are not the same number

The number printed on a bow's limb sticker is an AMO draw length, the measurement standard the industry publishes through the ATA Technical Guidelines. It is defined as the distance from the nock point on the string to the pivot point of the grip at full draw, plus 1.75 inches. The bare distance, nock to pivot, is the true draw length. The added 1.75 inches stands in for the depth of the riser behind the pivot point, which keeps bow ratings comparable across thick and thin grips.

Two consequences follow. First, bows are rated for draw weight at 28 inches AMO, so a 60 pound limb sticker assumes that exact distance. Second, the wingspan formulas already land on the AMO scale, so never add 1.75 inches to a wingspan estimate. Add it only to a measured nock to pivot number, which is what the measured box in the calculator does.

How to measure your wingspan at a wall

The measurement takes two minutes and one helper. Stand with your back flat against a wall, shoes off, arms stretched out to the sides at shoulder height and palms facing the wall. Your helper marks the wall at the tip of each middle finger, then measures straight between the two marks along the wall. Face the wall with palms flat on it if that feels steadier; the reading is the same as long as the arms stay level and the shoulders stay relaxed.

• Do not stretch. Reaching for extra length is the single most common error, and half an inch of stretch becomes half an inch of draw length you cannot hold.
• Mark the tip of the middle finger, not the fingernail edge or the wrist crease.
• Measure twice and keep the average. A reading that moves more than a quarter inch between tries means the arms moved.
• Round to the nearest quarter inch and enter that.
• If your tape reads centimeters, enter centimeters and pick centimeters in the unit box. The calculator divides by 2.54 for you, so a 178 cm wingspan is 70.1 inches.

Height is a fair backup when no helper is around, because wingspan and height land within an inch or two of each other for most adults. A person 5 feet 10 inches tall is about 70 inches fingertip to fingertip, which points to a 28 inch draw.

Turning draw length into arrow length

Arrow length is measured from the bottom of the nock groove to the cut end of the shaft, and the point or insert is not part of the number. Most adult setups run 1 to 3 inches longer than the draw length. The margin keeps the shaft clear of the arrow rest and the front of the riser at full draw, and it leaves room for the form changes every new archer goes through. Arrow makers such as Easton describe the measurement as marking an extra long arrow about 1 inch in front of the most forward point of the rest and cutting there, which is why the Easton archery FAQ defines correct arrow length from the nock groove to the cut shaft.

The floor matters more than the ceiling. An arrow cut to the exact draw length can fall off the rest at full draw, and a short arrow can end up behind the hand holding the bow. When the estimate sits between two whole sizes, cut to the longer one; arrow length comes off with a saw but never goes back on.

Bow types, draw weight and the 28 inch yardstick

Compound bows hold a fixed draw length, set by a cam module or a draw stop in half inch steps across a range the maker publishes, and a shop sets it once to your number. Recurve and longbow limbs have no fixed length at all; they are rated at 28 inches AMO and pull harder the further you draw. The published correction is one twentieth of the rated weight per inch, so a 50 pound recurve pulled to 30 inches is about 55 pounds on the fingers, and pulled to 26 inches it is about 45.

Grow-with-them bows exist too. The National Archery in the Schools Program fits students with a single bow adjustable from 11 to 20 pounds at any draw length, which is why school programs can hand the same bow to a fifth grader and a senior. For hunting, weight is regulated: the Archery Trade Association recommends a 30 pound minimum for typical big game and counted 33 of 50 states setting one, with 30, 35 and 40 pounds the figures used for whitetail. Rules differ state by state, so check your own:

Four mistakes that cost money at the bow shop

Adding 1.75 inches twice. A wingspan estimate already lands on the AMO scale. Add the 1.75 inches only when you measured from the string to the grip pivot, and the calculator keeps the two paths separate.

Stretching the tape. Reaching for a longer mark inflates wingspan, and a half inch of stretch becomes a bow set half an inch long. At full draw an overlong draw shows up as a bowed bow arm, a floating anchor and groups that wander left and right.

Ordering a fixed draw length before measuring. Many compounds are sold with a module that sets draw length in half inch steps. Buy the model whose range brackets your estimate, then let a shop fine tune it at full draw with a draw arrow or draw board.

Guessing a kid's length from last year. Children grow about 2 to 2.5 inches of height a year through the middle school years, and wingspan follows. Re measure every season; the adjustable 11 to 20 pound school bow exists for a reason, and a fixed youth bow bought long will be shot with a collapsed form by spring.

Three archers, start to finish

Archer A stands 5 feet 10 inches tall with a 70 inch wingspan. Divided by 2.5, the estimate is 28.0 inches, the rounded number a shop would set, and the subtract 15 rule lands at 27.5 as a check. Arrows run 29.0 to 31.0 inches, and a 50 pound recurve rated at 28 inches pulls 50 pounds.

Archer B measures 64 inches fingertip to fingertip. The estimate is 25.6, which rounds to 25.5 inches of draw, so arrows go 26.5 to 28.5 inches and the same 50 pound rated recurve pulls 50 + (50 / 20) x (25.5 - 28) = 43.75 pounds at that length. The bow is lighter than the sticker because the draw is short.

Archer C skipped the estimate and had a shop measure 27.00 inches from string to grip pivot. Adding 1.75 inches gives a 28.75 inch AMO draw, arrows at 29.75 to 31.75 inches, and the 50 pound bow pulls 51.88 pounds. One measured number beat two estimates, which is the order of authority the calculator follows whenever the measured box is filled.