What is the maximum power consumption (in mW) of the Arduino Nano 3.0, when it is running in its default state (at 16MHz, no LEDs removed) and powered by an external regulated 5V supply so it bypasses the built in voltage regulator?

This will give us an upper bound on the power consumption of the Arduino Nano that can be used during estimates.

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  • 1
    In this line of the answer: So depending on how much you use the serial port, and the leds I would guess around (2.4 + 15 + 4*4) = 33.4 mA I don't really get why you multiply 4*4, wouldn't it be 2*4?
    – user13180
    Sep 4, 2015 at 12:30

4 Answers 4


Well, it depends on what you have attached to the Arduino. If you are using the pins to do things you will definitely require more current.

If you ONLY want to power the Arduino, then I calculated what I think it should be below. (You should also check with someone who owns this device for an experimental value, and not just a calculated value. )

Based on the datasheet (fig 30-8, p 319), I would say the the processor will draw around 2.4 mA at 5 volts.

The USB chip draws around 15 mA depending on several things (p 18) http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

Then you have 2 LEDs with 680 ohm resistors. (Assuming 2 volt drop for each led) (5-2)/680 = around 4 mA per led.

So depending on how much you use the serial port, and the LEDs I would guess around (2.4 + 15 + 4*4) = 33.4 mA

33.4 mA * 5V = 0.167 Watts

I suspect you want to know to the total amount of power the Arduino can source, which is a bit harder to calculate.

The pins can provide up to 200 mA. (p 303 http://www.atmel.com/images/doc2545.pdf) So 33.4 + 200 = 233.4

I would also add a 20% safety margin (around 50 mA)
So I would want a 280 mA supply, if I was going to attach the Arduino to different things.

280 mA * 5 = 1.4 Watts

Let me know if my numbers are way off.

P.S.: Be careful making your own supply. It is critical that the voltage be very stable. An unstable supply can/will destroy an Ardiuno. I suggest using a linear regulator, like the LM7805. or maybe the LM317

  • 7805 and 317 both peak initially at 6V when first powered up from f.x. 12V. Doesn’t destroy my boards though.
    – user2497
    Dec 21, 2017 at 17:18
  • @user13180 - clamp with a Zener and use a cap
    – Peter Wone
    Feb 15, 2019 at 10:39
  • does the usb draw that much if it is used nly to power the board? DO you have a good library to put Nano to sleep? Thanks
    – Amir
    Mar 19, 2019 at 12:44

Yes, the i/o can source 40mA @ 5v (or 3v3) per pin, but the limit is'nt 40mA from each pin simultainiously but the limit is the processors dissipation. Read the 328A data sheet carefully and the truth will become clear.


From website https://store.arduino.cc/usa/arduino-nano: Each of the 14 digital pins on the Nano can be used as an input or output. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA. Therefore i would assume maximum power consumption is 14 x 40mA x 5V = 2.8W, depends on the board effeciency %, for example let's say 80%, so input could be 3.5W, but again you rarely use all 14 pins at once as outputs hence it is way way lower than 3.5W.This is just a ballpoint figure.

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    If an individual pin can provide 40mA, it does't mean that they can provide 560mA at once.
    – gre_gor
    Dec 18, 2017 at 17:01

"Each of the 14 digital pins on the Nano can be used as an input or output."

There are 6 analog input pins which are also digital pins, you must take those into account.

However, Note 3 under Table 32-2 of the '328P datasheet says: "Although each I/O port can source more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed:

3.1. The sum of all IOH, for ports C0 - C5, D0- D4, ADC7, RESET should not exceed 100mA.

3.2. The sum of all IOH, for ports B0 - B5, D5 - D7, ADC6, XTAL1, XTAL2 should not exceed 100mA.

(but ADC6 and ADC7 are analog input only, and should not be sourcing current)

So I would suggest that to keep your Nano healthy, 200mA x 5V = 1W be considered for the IO, and then the amounts noted above for the Power LED, L LED (which is driven by D13), and internal running of the chip be taken into account.

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