Hole saw sizes: the chart, and which one for your job

A hole saw is a toothed cup that mounts on an arbor in a drill and cuts a circle, leaving a plug in the middle instead of turning the whole core into sawdust. The confusion around hole saw sizes never comes from the saw itself: the size stamped on the cup is the diameter of the hole it cuts, close enough for every field purpose. The confusion comes from the jobs, because conduit, pipe, and door hardware are all named in nominal sizes that are not their real diameters. This page gives the standard size chart, then the trade-specific mappings electricians, plumbers, and door installers actually need, with the sources behind every number.

The standard size range

Bi-metal hole saws run from 3/4 in (19 mm) up to about 6 in (152 mm) in most catalogs, with carbide-grit and diamond cups extending the range for tile, stone, and very large holes. The sizes a general-purpose kit clusters around, per Engineer Fix's hole saw guide and the Morse hole saw kit specifications: 3/4, 7/8, 1, 1-1/8, 1-1/4, 1-3/8, 1-1/2, 1-3/4, 2, 2-1/8, 2-1/4, and 2-1/2 in, with 3 in and up available individually. Morse, a hole saw manufacturer since the original saw patents, sells trade kits built around exactly these steps: their electrician kit runs 7/8 to 2-1/2 in, their locksmith kit 7/8 to 2-1/8 in, and their plumbing kits 3/4 in through 4-1/2 in.

Hole saw sizes for EMT and other conduit

This is the mapping that trips everyone up, because the hole is never the size of the conduit. Conduit trade sizes are nominal, and the hole must pass the connector body and its locknut, not the tube. The 1/2 in EMT connector that started this whole lookup needs a 7/8 in hole, not a 1/2 in hole. The chart below matches the NEMA knockout standard that connector manufacturers build to, cross-checked across three independent references: the Shielden conduit hole saw chart, American Fittings' NEMA hole size table (publishing the NEMA knockout diameters directly), and Mr Electrician's conduit hole saw reference.

Notes from the same sources: EMT, rigid (RMC), IMC, and PVC conduit all use the same trade-size chart, because the knockout standard is uniform across conduit types. For 1/2 through 1 in there is a field rule of thumb, hole saw size equals trade size plus 3/8 in, but it drifts at larger sizes, so use the chart above 1 in. When the fit genuinely matters, the locknut or connector manufacturer's stated knockout diameter is the controlling number. And in panel work, a knockout punch makes a cleaner hole than a saw in thin steel; the saw wins on portability and thick or already-mounted enclosures.

Hole saw sizes for plumbing

Plumbing hole sizing runs on actual outside diameters, and plumbing's nominal sizes are as misleading as conduit's. Copper is the clean case: Type K, L, and M copper all share the same OD at a given nominal size, and the OD is exactly 1/8 in larger than the name. A 1/2 in copper tube is 0.625 in OD, 3/4 in is 0.875 in, 1 in is 1.125 in, confirmed by the Turn2 Engineering copper size chart (ASTM B88 basis) and Petersen Products' copper tubing table. So a hole that passes 1/2 in copper with clearance is a 3/4 or 7/8 in saw, 3/4 in copper wants 1 in or 1-1/8 in, and 1 in copper wants 1-1/4 in. PEX and CPVC follow their own ODs; measure the pipe, do not trust the nominal name. For running pipe through studs and plates, plumbers drill one size up from the pipe OD for wiggle room, which is why trade plumbing kits step in 1/8 and 1/4 in increments from 3/4 through 2-1/2 in.

One honest correction to a number that circulates online: there is no single standard shower valve hole saw size. A valve rough-in opening is set by the valve's plaster guard, not by a hole saw chart. Delta's own instruction for the ubiquitous R10000 MultiChoice rough is to cut the opening to the plaster guard, a 4 in square, per Delta's product Q and A and the R10000 installation manual; other brands fall between roughly 2-1/2 and 3-1/4 in round depending on model. The escutcheon must cover the hole, so oversizing is the unrecoverable error: always the valve model's own instruction sheet, never a generic chart, including ours.

Hole saws for doors and locks

Door hardware is the one domain with a true industry-standard answer, stated identically by Engineer Fix and by Morse's dedicated lock-install kits: the bore for a door knob, lever, or deadbolt cylinder is 2-1/8 in (54 mm), and the edge bore for the latch mechanism is 1 in (25 mm). Morse sells a two-saw lock kit containing exactly those two sizes. Bore the face hole first with the door clamped, then the edge hole meeting it; a brad-point or spade bit can do the edge bore, but the 2-1/8 in face hole needs the saw.

Hole saws for wood

Wood is the least fussy material: any bi-metal saw cuts it, and the size is simply the hole you want, for cable pass-throughs, can lights, duct, hoses, or speaker holes. The practical constraints are depth and power. Standard hole saw cups cut about 1-1/2 to 1-15/16 in deep (Morse quotes 1-15/16 in across their bi-metal line), so thicker stock needs a deep-cut saw or drilling from both faces. And a big saw in a weak drill just stalls: a 2-1/2 in cup through dense stock asks real torque of the motor. Our torque settings explainer covers what the numbers mean, and the comparison table shows which drills in each class carry the most verified torque. If the saw chatters or grabs, your drill's speed is too high for the diameter; drop to low gear. Chuck side, every hole saw arbor fits the 1/2 in chucks standard on 18V/20V class drills, a sizing story covered in chuck sizes explained. For the arbors themselves, the two cup threads and which shank fits which chuck: see the hole saw arbor size chart.

Using one without wrecking it or the work

• Pilot drill first: the arbor's pilot bit centers the cup; let it lead before the cup teeth touch.
• Slow for diameter: big cups want low RPM, especially in steel. Smoke means too fast or too dry.
• Lubricate steel: cutting oil on metal enclosures; nothing in wood.
• Clear the plug: the spent core jams the cup and kills cutting speed; push it out through the side slots between holes.
• Orbital for thick stock: a gentle swirling motion helps cooling in deep cuts, the same trick tile guides recommend for diamond cups, which brings up materials: hole saws also exist in carbide-grit and diamond versions for tile, glass, and stone, and those follow the cooling rules on our how to drill into tile page, not the wood rules here.

Quick answers

• What size hole saw for 1/2 inch conduit? 7/8 in. The hole passes the connector, not the tube; 3/4 in conduit takes 1-1/8 in and 1 in takes 1-3/8 in.
• What size for a deadbolt? 2-1/8 in for the cylinder bore in the door face, 1 in for the latch bore in the edge. These are the industry-standard lockset sizes.
• What size for a shower valve? Whatever the valve's instruction sheet says: the opening is set by the plaster guard, commonly around 2-1/2 to 4 in, and it varies by brand and model. There is no universal hole saw size for valves.
• What size for 1/2 inch copper pipe? 3/4 or 7/8 in: 1/2 in copper is actually 0.625 in OD, so anything that clears that with room to move.
• Do I need a special saw for metal boxes? Bi-metal is standard for sheet-metal enclosures; carbide-tipped lasts longer in heavy use. For thick steel panels, knockout punches make the cleaner hole.

Related guides

Also on this site: drill chuck sizes explained for what the arbor needs from your drill, drill torque settings explained for driving big cups without stalling, drilling into tile for the diamond-hole-saw side of the family, and step drill bit sizes for the thin-sheet holes that need a cone, not a saw. For the wood-only side of big holes, wood boring bits compared covers when a spade bit or Forstner beats the saw, and the drill press speed chart carries the low RPMs a big saw in steel demands.