Number drill bit sizes
Wire-gauge style number sizes (#) — the labels stamped on many jobber sets between fractional steps. Each row lists the number label, decimal inch, and millimeter equivalent so you can match a tap chart or worn stamp without opening the full four-system chart. Need fractional, metric, or letter? Use the links below or the flagship chart.
Full size chart · Size finder · Drill hub · Fractional · Metric · Letter
How to use this table
Scan the Size column for the # mark on the bit or the number on a tap-drill chart. Decimal inch and mm are nominal workshop values for comparison — not lab certification. Click Find on a row to open the size finder with that label preselected. Shopping and kit cards live on the tool page. Number labels are usually outside the Wave0 mapped fractional kit chips; expect honest default-kit notes when a # size is not on the lid map.
Remember the gauge direction: larger number → smaller diameter (#52 is much smaller than #1). That trips people who treat “higher” as “bigger.” If a plan says #21 and your case only prints fractions, use decimal inch to find the nearest fractional neighbor, then decide whether nearest is good enough for the material.
Typical flow: read the number from the chart or stamp, find the row, cross-check mm if you hold a metric bit box, then Find → size finder. This split stays a quiet reference so the flagship chart and finder own navigation and commerce. Critical tap and reamer work still needs the bit and a gauge — do not treat the table as a code guarantee.
Coverage here is the verified anchor set in our dual-sourced data (status=ok), not a claim that every #1–#80 industrial step is already listed. Missing long-tail numbers can be added in later data waves without changing the Find → kit path. Hub money CTAs stay on mapped fractionals so we never promote an unmapped # size as if the default kit lid includes it.
FAQ
What are number drill bit sizes?
Number sizes use a wire-gauge style label such as #7 or #21. Higher numbers are smaller diameters. They sit between fractional steps for tighter pilot and tap-drill work.
Is this the full #1–#80 series?
No. This page lists the verified number rows in our current dual-sourced table (common shop anchors, not every gauge). Rows shown are status-ok reference data — not placeholder seeds. The full industrial series can expand in later waves without changing how Find works.
How do number sizes relate to fractional bits?
Number sizes fill gaps between fractions. Example: #7 is about 0.2010" (near 13/64"), useful when 3/16" is small and 1/4" is large. Use decimal and mm columns to compare, then open the full chart if you need neighboring systems.
Where do I shop a set that includes a number size?
Click Find on a row to open the size finder with that label. Many consumer kits map fractional lids only; number labels may resolve to a default set with an honest note when not explicitly mapped.
Sources
Number diameters follow common published wire-gauge drill indexes used in workshop references. Values are nominal. Confirm critical fits on the bit or with a gauge. See the site disclaimer for limits of use.