Enter any size in any system. The page shows where it falls in every series and which bit is closest above and below it. You can also check the sizes against a real bit at true scale.
The axis is log scale, so a #60 drill and a 2-1/2″ hole saw fit on one chart with even spacing. Click or drag anywhere to move the target. The shaded band is the range shown in the zoomed view below.
Linear scale around the target. Every size in range is labeled, and the closest one in each series has a dark ring.
The closest bit at or under the target, and the closest at or over it. Under is the usual choice for a tap drill or a tight fit; over is the usual choice for a clearance hole. Click any size to make it the target.
Each circle is drawn at true diameter and shows the closest size in each series, for series that have a size inside the zoom window. The dashed ring is the target size, so you can see how much each bit is over or under. Set the scale once and you can hold a bit up to the screen.
Metric sizes are converted to inches at 25.4 mm/in. Input rules:#nis a number drill, a single letter is a letter drill, fractions like17/64or1-3/8are inches, a value ending inmmis millimeters, and a plain number is inches up to 3, millimeters above that. Check a machinist's handbook before relying on these numbers for critical tolerances.