Electrical Conduit Hole Saw Sizes

See the Hole Saw List Below

Some of my hole saws and arbors
Some of my hole saws and arbors


Dear Mr. Electrician: What are the actual hole saw sizes for the various trade sizes of electrical conduit?  I plan to install a lot of electrical conduit.  I know that I will need to drill with hole saws or use a knockout punch in junction boxes and the circuit breaker panel.

Answer: I have posted the hole saw and knockout sizes for electrical conduit below.  For electrician’s hole saw kits see here.  When drilling with a hole saw it is important to use a slower spinning drill with a lot of torque rather than a high speed drill.  It is best to drill at 400 revolutions per minute (RPM) or slower when using a hole saw.  Drilling at a slower speed will help the hole saw last longer, and there is less of a danger of the hole saw getting jammed and causing damage.  NOTE: Text links go to applicable products on Amazon.com

I usually use my Milwaukee 1/2″ Right Angle Drill when using a hole saw as the torque is very good and the RPM’S are just right.  The extra length of the right angle drill makes it easier to maintain control of the drill if the hole saw does get jammed.  I suggest wearing work gloves when using a right angle drill.

When drilling into metal, it is a good idea to oil the hole saw a few times to prevent premature wearing of the hole saw teeth.  I read in a trade magazine of one electrician who puts an oil soaked cut-to-size piece of Felt inside of his hole saws whenever he drills into metal.  As the hole saw heats up from drilling, the oil will trickle down onto the metal being drilled.  Put something on the floor to protect it from oil leaks such as flattened boxes or an old piece of plywood.  Although you can probably use most general purpose or motor oils for lubricating when drilling, there are oils made especially for drilling, tapping, and threading.  Amazon sells cutting oil which is used for these purposes.

Hole saw arbors and pilot drill bits. Two types of hole saw arbors are depicted and they are not interchangeable
Hole saw arbors and pilot drill bits. Two types of hole saw arbors are depicted and they are not interchangeable.  The three arbors on the top left can only be used with a hole saw that has the rectangular round shape.  The others screw in to one of two standard size threads.

Electrician’s Hole Saw Sizes:

For 1/2″ conduit, drill using a 7/8″ hole saw or 1/2″ conduit knockout punch (.885″ or 22.5mm).

For 3/4″ conduit, drill using a 1 1/8″ hole saw or 3/4″ conduit knockout punch (1.115″ or 28.3mm).

For 1″ conduit, drill using a 1 3/8″ hole saw or 1″ conduit knockout punch (1.362″ or 34.6mm).

For 1 1/4″ conduit, drill using a 1 3/4″ hole saw or 1 1/4″ conduit knockout punch (1.701″ or 43.2mm).

For 1 1/2″ conduit, drill using a 2″ hole saw or 1 1/2″ conduit knockout punch (1.951″ or 49.6mm).

For 2″ conduit, drill using a 2 1/2″ hole saw or 2″ conduit knockout punch (2.416″ or 61.5mm).

For 2 1/2″ conduit, drill using a 3″ hole saw or 2 1/2″ conduit knockout punch (2.914″ or 74mm).

For 3″ conduit, drill using a 3 5/8″ hole saw or 3″ conduit knockout punch (3.539″ or 89.9mm).

For 3 1/2″ conduit, drill using a 4 1/8″ hole saw or 3 1/2″ conduit knockout punch (4.044″ or 102.7mm).

For 4″ conduit, drill using a 4 1/2″ hole saw or 4″ conduit knockout punch (4.544″ or 115.4mm).

For 5″ conduit, use a 5 1/2″ hole saw.

For 6″ conduit, use a 6 5/8″ hole saw.

Electrical Conduit Trade SizeHole Saw Size
For Conduit or Fitting
Drill or Hole Saw Size For
NPT Tapered Threaded Tap.
Taper is 3/4"per foot.
Tap Thread Size
1/8" Pipe or Fixture Nipple13/32"Q (21/64" or .332")27 Threads Per inch
1/4" Pipe or Fixture Nipple35/64"7/16"18 Threads Per Inch
3/8" Pipe or Fixture Nipple43/64"9/16"18 Threads Per Inch
1/2" or 16mm Conduit7/8" or 22mm45/64" 14 Threads Per Inch
3/4" or 21mm Conduit1 1/8" or 28mm59/64" or 7/8"14 Threads Per Inch
1" or 27mm Conduit1 3/8" or 34mm1 5/32" 11.5 Threads Per Inch
1 1/4" or 35mm Conduit1 3/4"1 1/2"11.5 Threads Per Inch
1 1/2" or 41mm Conduit2"1 47/64"11.5 Threads Per Inch
2" or 53mm Conduit2 1/2"2 7/32"11.5 Threads per Inch
2 1/2" or 63mm Conduit3"2 5/8"8 Threads per Inch
3" or 78mm Conduit3 5/8"3 1/4"8 Threads per Inch
3 1/2" or 91mm Conduit4 1/8"3 3/4"8 Threads per Inch
4" or 103mm Conduit4 1/2"4 1/4"8 Threads per Inch
5" or 129mm Conduit5 1/2"5 9/32"8 Threads per Inch
6" or 155mm Conduit6 5/8"6 11/32"8 Threads per Inch

Some hole saws with broken and worn down teeth

Some hole saws with broken and worn down teeth

Click For Electrical Conduit Dimensions:

1/2″ (16)        3/4″ (21)        1″(27)

1 1/4″ (35)        1 1/2″ (41)        2″ (53)

2 1/2″ (63)         3″ (78)        3 1/2″ (91)

4″ (103)          5″ (129)         6″ (155)

See my post describing various electrical conduit types.

My old html conduit dimensions table can be seen here.