An LED needs a series resistor to limit its current to a safe level. Set the supply voltage, the LED color, and a resistor value, then read the current through the LED and whether it lands in the 10 to 20 mA operating range.
Supply voltage
LED color
Forward voltages and the 25 mA maximum forward current are from Simon Monk, Hacking Electronics, 2nd ed., Table 4-1 “An LED Datasheet”, p. 55. A part’s own datasheet governs; check it before you build.
Series resistor
Ω
Select supply, LED color, and resistor, then press Calculate.