How to Measure a Bandsaw Blade: String Method + Real Math
To measure a bandsaw blade, wrap a piece of string or a cloth tape around both wheels following the exact path the blade takes, mark where it overlaps, then measure that length flat. If you don’t have the old blade to wrap, you can calculate the length instead: measure the diameter of one wheel and the center-to-center distance between the two wheel axles, then use the formula 2 × center distance + (π × wheel diameter).
Either method gets you a usable number, but the size charts that list a single blade length per throat size (“10-inch saw = 70.5 inches,” “14-inch saw = 93.5 inches”) are only sometimes right – the same 14-inch saw can take two completely different blade lengths depending on one detail almost nobody checks first.
Two Ways to Measure a Bandsaw Blade
Best for Confirming Blade Width & Alignment
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Method 1: Wrap and Measure (You Have a Blade or String)
- Unplug the saw and open the wheel covers.
- If you still have the old blade, mark one tooth with a paint pen so you know your start and end point.
- Lay a length of string, mason’s line, or a cloth tape along the exact path the blade travels – over the top wheel, down and around the bottom wheel, and back – keeping it snug against both wheel rims, not pulled straight across the gap.
- Mark or pinch the point where the string meets your starting mark.
- Lay the string flat and measure it end to end with a tape measure. That number is your blade length.
No old blade and no string long enough to reach around both wheels at once? Roll the blade (or a length of string) along the floor for one full revolution instead: make a chalk mark on the blade and a matching mark on the floor, roll it until the mark returns to the floor, and measure the straight-line distance between the two floor marks.
Method 2: Calculate It From Wheel Diameter and Center Distance
If there’s no blade on the saw at all, you can get the length from two measurements: the diameter of a wheel, and the center-to-center distance between the upper and lower wheel axles (not the gap between them – the distance between their centers).
The formula for a standard two-wheel bandsaw with equal-size wheels is:
Blade length = (2 × center-to-center distance) + (π × wheel diameter)
For example, a saw with an 18-inch center distance and 14-inch wheels works out to (2 × 18) + (3.14159 × 14) = 36 + 43.98 = about 80 inches. Round to the nearest common stock length (most suppliers sell in half-inch increments), and order that size.
Why “12-Inch Saw = 80-Inch Blade” Charts Get It Wrong
Blade-length charts are built around throat size (the “12-inch” or “14-inch” in a bandsaw’s name), but throat size only describes how far a piece of wood can extend from the blade to the frame – it says nothing about how far apart the wheels sit. Two saws with the identical throat capacity can have completely different center-to-center distances, which changes the blade length even though the saw is marketed under the same size.
The clearest real example is the classic Delta/Rockwell-style 14-inch bandsaw: the same saw takes a 93.5-inch blade in its stock configuration, or a 105-inch blade once a riser block is bolted in to add resaw height. The throat size never changed – it’s still a “14-inch” saw either way – but the wheels moved farther apart, so the blade has to be longer. A chart that lists one number for “14-inch bandsaw” is right for exactly one of those two configurations and wrong for the other.
The takeaway: treat any generic size chart as a starting estimate, not a final answer. If your saw has ever had a riser block added, or if you’re not certain it’s in its factory-stock configuration, measure it directly with Method 1 or 2 above instead of trusting the throat size alone.
Measuring Blade Width and Thickness
Length gets a blade to fit the wheels; width and thickness determine what kind of cutting it can actually do. Measure width across the flat back-to-front of the blade with a ruler or caliper – most bandsaws run anywhere from 1/8 inch (tight scroll and curve work) up to 3/4 inch or more (resawing and straight ripping) on larger saws. Thickness matters just as much and is easy to get wrong by eye: use a caliper or micrometer across the flat of the blade body, not across the teeth. Most hobbyist bandsaw blades run between 0.020 and 0.032 inches thick; going thicker than your saw’s wheels are rated for adds strain the tires and bearings weren’t built for, even if the blade otherwise fits.
Checking Blade Tension After Installing a New Blade
A correctly measured blade still needs correct tension to cut straight. Most saws have a built-in tension scale on the upper wheel housing calibrated for a specific blade width, but those factory scales are notoriously approximate. A quick manual check: with the guides backed off, push sideways on the blade at the midpoint between the wheels. A properly tensioned 1/2-inch blade should deflect somewhere around 1/4 inch under moderate finger pressure – noticeably less deflection than that and the blade is likely over-tensioned, noticeably more and it’s under-tensioned and will wander or drift during a cut. Narrower blades deflect more at the same tension than wider ones, so use the deflection test as a relative check against how the same blade felt when it was cutting well, not as an absolute number. For a deeper look at getting this setting right, see our guide on how tight a bandsaw blade should be.
Storing a Blade So It Keeps Its Shape
A blade that’s been coiled correctly for storage goes back onto the wheels without a fight; one that’s been jammed into a box loose will fight the wheels the whole time it’s mounted. Coil the blade into three even loops by twisting it against its natural curve (the same motion as coiling an extension cord), wipe off resin and sawdust with a dry rag first, and hang it or lay it flat rather than standing it on edge, which stresses the weld point. A light film of paste wax or a rust-inhibiting oil on the blade body before storage keeps a spare blade from surface-rusting in a humid shop, which is the most common reason a “new” spare blade shows up pitted the one time it finally gets used.
Frequently Asked Questions
What size bandsaw blade do I need?
Measure your saw directly rather than relying on throat size alone: wrap a string or tape around both wheels following the blade’s path (Method 1), or measure wheel diameter and center-to-center distance and calculate it (Method 2). Throat size alone can be misleading if a riser block or non-standard wheel spacing is involved.
Why do two 14-inch bandsaws need different blade lengths?
Throat size describes cutting capacity, not wheel spacing. A classic 14-inch Delta/Rockwell-style bandsaw takes a 93.5-inch blade stock, or a 105-inch blade once a riser block is added to increase resaw height – the wheels move farther apart even though the saw is still called a 14-inch model.
How do I measure bandsaw blade width and thickness?
Measure width across the flat of the blade, back to front, with a ruler or caliper. Measure thickness across the flat blade body (not across the teeth) with a caliper or micrometer. Most hobbyist blades run 1/8 to 3/4 inch wide and 0.020 to 0.032 inches thick.
Can I measure a bandsaw blade without removing it?
Yes. With the wheel covers open, you can wrap a string or tape around the mounted blade following its path without taking it off the saw, then measure the string flat. This works as well as removing the blade and is faster if the blade is still usable.
