Sizing
How many amps does a machine shop need in a garage
The machine shop package that fits a 22 x 22 ft garage needs 5 circuits (0 at 240V), about 22 A of demand on a 240V-equivalent basis, and a 60 A subpanel to ask your electrician about.
The circuit list
| Circuit | Volts | Breaker | Wire | Receptacle |
|---|---|---|---|---|
| 10 x 22 metal lathe | 120 V | 20 A | 12 AWG | NEMA 5-20R |
| 7 x 27 mill/drill | 120 V | 20 A | 12 AWG | NEMA 5-20R |
| 20 gallon compressor | 120 V | 20 A | 12 AWG | NEMA 5-20R |
| Shared bench circuit 1 | 120 V | 20 A | 12 AWG | NEMA 5-20R (several) |
| Shared bench circuit 2 | 120 V | 20 A | 12 AWG | NEMA 5-20R (several) |
240V machines each get a dedicated circuit sized at 125 percent of their running amps; 120V machines at 10 A or more get their own 20 A circuit; small loads share bench circuits. Wire is copper on the NM-B ampacity column (NEC Table 310.16, 60 C). These are planning sizes: a licensed electrician confirms every one.
Why that subpanel
Connected load adds to 30 A in 240V-equivalent terms, but a shop rarely runs everything at once: counting the largest load in full and the rest at a diversity factor gives about 22 A, and with the 125 percent rule a 60 A subpanel. The package is: Lathe 10x22, Mill/drill, 6 ft bench, Tool bench, Tool chest, Lathe 9x19, Shelving, Compressor. Lathe, mill, drill press, grinder and a heavy bench on a slab that can take it.
Use the workshop amps calculator to change the machines, and open the 22 x 22 machine shop layout to see where each one sits.
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Get the garage shop planning checklist
One printable page: measure the bay, count the circuits, list the machines, check the floor. Plus a few short emails, then a couple a month at most.
Unsubscribe anytime. You can also just read the checklist on this site.Subpanel by trade: the other answers
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Frequently asked questions
Do I need 240V for a machine shop?
Not for the machines in this package: they all run on 120V. Heaters, large compressors, collectors over 2 HP and most welders are happier on 240V; the 240V circuit calculator sizes each.
This page is researched guidance, not professional electrical, engineering or safety advice. Circuits, loads and clearances depend on your house, your service and your town: have a licensed electrician confirm any wiring, and check local code and each manufacturer's manual before you act.
