Reference family
Drill bit sizes
Fractional, metric, number, and letter drill bit sizes with decimal and millimeter equivalents. Look up a label, then open a set that includes it.
Start here
Already know the label? Use the finder. Browsing every size? Use the chart.
Size finder
Pick a system and label. Get decimal + mm, then a matching set.
Open finder → Size convert
Convert a label across fractional, metric, number, and letter systems.
Open convert →
Printable size chart
Shop-wall printable of all four systems — clean print layout.
Open printable →
Drill bit for a screw
Pilot and clearance holes for wood and machine screws.
Open →Quick convert
Approximate inch ↔ mm. For full label lookup use the size finder or size convert tool.
Browse by topic
Four labeling systems, one diameter idea. Open a series, or the combined chart.
Flagship chart
Full drill bit size chart
All four systems in one reference table with Find links into the size finder.
How it works
Spec → label → set that includes the size you looked up.
- 1
Look up the size
Finder, chart, or convert — get a clear label.
- 2
Confirm inch / mm
Same diameter idea across fractional, metric, number, and letter.
- 3
Shop a set that includes it
Kit card appears after a label is selected.
FAQ
Size convert → Common questions
Systems · convert · kit
What are the four drill bit size systems?
Fractional (inch fractions like 1/4"), metric (mm), number (#1–#80), and letter (A–Z). Use the chart for the full list, or open a system page for one series.
How do I convert a fractional size to decimal?
Divide the fraction — 1/4" = 0.2500". The size finder and chart list decimal inch and mm for every label we carry.
Number vs letter bits — which is larger?
Number bits fill many small steps between fractions. Letter bits sit larger (A is bigger than most common number sizes). When a fraction is too coarse, check number or letter.
How are metric drill bit sizes defined?
By diameter in millimeters (e.g. 3mm, 6.5mm). Open the metric table or the finder to compare inch equivalents.
Match screws to drill bits
Pilot holes and tap drills under Fasteners when you need the hole for a given screw.