How many 20 amp plugs can I use in a workshop on a 20 amp breaker?
For a workshop attached to a dwelling, the NEC does not set a maximum number of receptacles on a 20 amp branch circuit. That surprises people, but dwelling receptacle loads are covered by the general lighting load calculation in 220.14(J), so ten or twelve receptacles on one 20 amp circuit is not a code violation. Whether it is a good idea in a shop full of motors is a different question.
The commercial rule of 13
In other than dwelling units, 220.14(I) assigns 180 VA per receptacle strap. A 20 amp, 120 volt circuit is 2,400 VA, and 2400 divided by 180 gives 13 receptacles. On a 15 amp circuit the same math gives 10. If your workshop is a commercial space, that is your ceiling. A duplex counts as one strap, a quad as two.
What actually matters in a workshop
Design to the loads, not the count. A table saw pulling 13 amps and a dust collector pulling 9 cannot share one 20 amp circuit while both running. Split the shop into at least two small appliance style circuits: one for the primary machine wall, one for chargers, lights on their own circuit so a tripped saw breaker does not leave you in the dark next to a spinning blade. Receptacles on 20 amp circuits can be 15 or 20 amp duplex devices per Table 210.21(B)(3), but a single receptacle on an individual branch circuit must match the circuit rating.
Protection requirements
NEC 2023 210.8(A) requires GFCI protection for all 125 volt through 250 volt receptacles in garages and accessory buildings at dwellings, and unfinished basements too. AFCI requirements under 210.12 depend on how the space is classified; a detached shop is typically outside AFCI scope while attached garage circuits generally need it in areas specified. Cord-connected stationary tools are fine on GFCI, and modern machines have largely stopped nuisance tripping.
Field notes
Wire the shop in 12 AWG minimum, put receptacles every 4 to 6 feet at bench height, and label the panel honestly. If a 240 volt machine is in the future, land a spare 2-pole space and conduit path now. The cheapest circuit you will ever install is the one added while the walls are open.