What is the maximum wattage of electric heaters that you can put on a single 20A circuit?

Not being an electrician, but having done a lot of wiring in my house (!), my thinking is that because the heaters are 240V, 80% capacity of 12-ga wire (20Amp) is 16 amps means that you could have 240*16 = 3840W of electric baseboard on one circuit. Is this correct?