Need some help check with calculation for Power P in W

hello everyone,
i designing pcb on eagle, while making schematic noticed have little space resistors 1/2w decided check if can use 1/4w made these calculation need please check if it's right ?

to limit brightness chose big values of resistor in advance

i have 3 kinds of leds these characteristics:
- blue: 3v, 18ma (advised current), decided right resistor value r=10 000 ohms equal brightness  

- red: 2v, 18ma (advised current), decided right resistor value r=1000 ohms equal brightness  

- green: 3v, 18ma (advised current), decided right resistor value r=100 000 ohms equal brightness  

-5v source shift register 595 output pins

my calculations :

- blue led:
vr = vcc - vled = 5 - 3 = 2v
i = v/r = 2/10 000 ohms = 0.0002a = 0.2 ma
p = i*i*r = 0.0002 x 0.0002 x 10 000 = 0.0004 w < 0.25w

- red led:
vr = vcc - vled = 5 - 2 = 3v
i = v/r = 3/1000 ohms = 0.003a = 3 ma
p = i*i*r = 0.003 x 0.003 x 1000 = 0.009 w < 0.25w

- green led:
vr = vcc - vled = 5 - 3 = 2v
i = v/r = 2/100 000 ohms = 0.00002a = 0.02 ma
p = i*i*r = 0.00002 x 0.00002 x 100 000 = 0.00004 w < 0.25w

you have errors,
resistor blue, assuming 5v source, 3v for vf, , 18ma desired current:
(5v - 3v)/.018a = 111 ohm, say you use standard value, 120 ohm
power dissipated resistor p = i*i*r = .018 *.018 * 120 = .0388w (38.8mw)
so 1/8w  (0.125w) or 1/4w (0.25w) rated resistor fine.

you can recheck rest.

Arduino Forum > Using Arduino > General Electronics > Need some help check with calculation for Power P in W

arduino