Bandsaw Blade Length Calculator (From Wheel Size and Centres)

The band saw’s manual is lost, the label on the old blade is worn off, and you need to order a new one. This calculator works out the blade length from two measurements you can take with a tape: the wheel diameter and the distance between the wheel centres. It handles saws whose upper and lower wheels differ in size, and it shows the shortest and longest blades the tension adjustment can take, so you know how much leeway you have when a stock length is close.

Bandsaw blade length calculator

How it works

A band saw blade is a belt round two pulleys. For equal wheels the length is the two straight runs plus one full wheel circumference:

equal wheels: L = 2 × C + π × D
unequal wheels (open belt): L = 2 × C × sin(θ/2) + r₁(2π − θ) + r₂θ, where θ = 2 × arccos((r₁ − r₂) ÷ C), r₁ is the larger wheel radius and C the centre distance

Measure C axle to axle with the upper wheel halfway through its tension travel: lowered fully for a new blade, raised fully for a stretched one. Moving the upper wheel by a distance changes the blade path by twice that distance, so a wheel with 1 in of travel fits blades from 1 in shorter to 1 in longer than the length at mid-travel.

Worked example

A saw with two 14 in wheels whose axles are 24-3/4 in apart with the tension set halfway, and 1 in of upper wheel travel:

Units: Inches
Upper wheel diameter: 14 in
Lower wheel diameter: 14 in
Distance between wheel centres: 24.75 in
Upper wheel tension travel: 1 in

The calculator gives:

Blade length: 93.48 in, 7′ 9-1/2" (2,374 mm)
Shortest blade that fits (wheel fully down): 92.48 in, 7′ 8-1/2" (2,349 mm)
Longest blade that fits (wheel fully up): 94.48 in, 7′ 10-1/2" (2,400 mm)
Blade wrapped on the wheels: 43.98 in, 3′ 8" (1,117 mm)
Straight runs (2 between the wheels): 49.5 in, 4′ 1-1/2" (1,257 mm)

The blade path is 2 × 24.75 + π × 14 = 93.48 in, so a 93-1/2 in blade fits at mid-travel, and anything from about 92-1/2 to 94-1/2 in can be tensioned. Riser blocks change C: a 6 in riser adds 12 in to the blade. If you measure C with a blade on the saw, measure with that blade tensioned, then subtract twice the distance the wheel has left to travel.

Blade length for equal wheels (inches)

Wheel	C 16 in	C 18 in	C 20 in	C 22 in	C 24 in	C 26 in	C 28 in	C 30 in
9 in	60.3	64.3	68.3	72.3	76.3	80.3	84.3	88.3
10 in	63.4	67.4	71.4	75.4	79.4	83.4	87.4	91.4
12 in	69.7	73.7	77.7	81.7	85.7	89.7	93.7	97.7
14 in	76	80	84	88	92	96	100	104
15 in	79.1	83.1	87.1	91.1	95.1	99.1	103.1	107.1
16 in	82.3	86.3	90.3	94.3	98.3	102.3	106.3	110.3
17 in	85.4	89.4	93.4	97.4	101.4	105.4	109.4	113.4
18 in	88.5	92.5	96.5	100.5	104.5	108.5	112.5	116.5
20 in	94.8	98.8	102.8	106.8	110.8	114.8	118.8	122.8

L = 2C + πD, with C the distance between wheel centres at mid-travel.

Notes and limits

Wheel diameter is measured over the tyres, the surface the blade runs on, not the casting.
The travel range tells you which stock lengths will fit. A length near the middle of the range leaves room for the blade to stretch in use.
Blade width and tooth pitch matter as much as length: narrow blades for tight curves, wide ones for resawing.
Motor and drive belt sizes for the saw itself: pulley speed and belt length calculator.

Frequently asked questions

How do I calculate bandsaw blade length?

For equal wheels, double the distance between the wheel centres and add π × the wheel diameter. Measure the centres with the upper wheel halfway through its tension travel.

What length blade for a 14 inch band saw?

It depends on the centre distance of your saw. At 24-3/4 in between centres, 14 in wheels need a 93-1/2 in blade; a 6 in riser block adds 12 in.

Can I use a blade that is a little short or long?

Yes, if it falls within the tension travel: the shortest blade fits with the upper wheel fully down, the longest with it fully up. The calculator shows both limits from the travel you enter.

How do I measure an old bandsaw blade?

Mark a tooth with chalk, roll the blade along the floor from the mark until the mark comes round again, and measure the distance. Or cut it and measure it straight.

Sources

Wikipedia, "Belt problem": length of an open belt round two pulleys, 2P sin(t/2) + r1(2 pi – t) + r2 t with t = 2 arccos((r1 – r2)/P)

Last reviewed: 25 October 2026. The calculation is covered by automated tests with known answers taken from the sources above. Found an error? Please let us know.