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Knowledge Base : Tools : Calculator | DC to AC amperage conversion run through an Inverter

Calculator | DC to AC amperage conversion run through an Inverter

So, you’ve got an electrical appliance to run, but no place to plug it in. When you need to run a regular household electrical type device in an area where no regular grid power is available, this calculator will help you figure out what size batteries and inverter you need!

Welcome to our DC/AC conversion tool (with inverter). This calculator is designed to assist you with power usage amounts, when converting from one power form to another using a DC to AC inverter. Just enter power numbers in the fields below, and we will do the calculations for you, including typical inefficiencies and all that other techie type stuff you may not care to calculate. If you are not sure of your numbers, have a look at the walkthrough illustrations below when entering numbers.

Enter AC Device Ratings
AC Voltage VAC
AC Amperage Amps AC (enter mAh as .xyz)
Wattage 0 Watts
DC Voltage   12 V     24 V     36 V     48 V
DC Amperage 0 Amps DC



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AC Voltage - Many applications will have a range of Input AC voltage. In the US, it can be anywhere from 100-125 VAC. In Europe, it's usually 200-240. For this example, we'll use the US standard of 120 Volts AC.

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AC Amperage - Input Amperage is how much current the application draws from the AC power. This number is usually rated in Amps. If the current is rated in milliamps (mAh) you can convert it to Amps by diving the number by 1000. For instance, our example application draws 300 milliamps, which is the same as 0.3 Amps.

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Wattage - Wattage is the total amount of power the application uses. It's calculated by multiplying voltage by amperage. Therefore the 120 VAC x 0.3 Amps equals 36 Watts.

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DC Voltage - Output Voltage is rating of your battery system, usually a single 12 volt battery. We use 12.5 volts for 12 volt battery systems.

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DC Amperage - Now we know that our application uses 36 watts of total power. If you take this power from a 12.5 VDC source, then the total amperage required increases to 3.31 Amps, or 3,310 milliamps. Since batteries have a limited capacity, or amp hours, it's important to size a battery large enough to handle the amperage demand for your application.

14 Responses,   4.7 Rating

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  • This was exactly what I was looking for. I would like to have the formula though just in case I need to do it the old fashioned way.

    October 31, 2012 a 2:47 pm
    • The calculator uses Ohm‘s Law. Watts = Volts x Amps. We additionally take into consideration an average inefficiency rate of 15% because the power is passing through an inverter. Once you find the watt amount from the AC volts x amps, you can divide the watts by DC volts to get DC amps, plus 15%. Without the efficiency loss, AC or DC watts will always be the same because it is total power. But as voltage goes up or down, in order to have the same power the amps will adjust accordingly.

      October 31, 2012 a 3:09 pm
    • Nice tool!
      Good idea to add the % of losses too!

      November 24, 2012 a 4:30 am
      • Nice tool

        November 28, 2012 a 8:20 am
        • When talking about current, for example if a device is drawing 3 amps, does that mean 3amps per hour?
          So if your drawing 3 amps from a 3amp/hour battery, that battery would last about 1 hour? Right?

          February 4, 2013 a 12:04 pm
        • VERY NICE TOOL.

          February 27, 2013 a 2:50 am
          • nice tool thanks for your information .can you explain about %loss calculation

            March 19, 2013 a 3:43 am
            • The loss figured is based upon the average efficiency for Pure Sine Wave power inverters. In this case, 15% loss, or 85% efficiency.

              Jeremy Fear
              March 19, 2013 a 10:31 am
            • DC to AC amperage conversion run through an Inverter.
              What is the correct explanation of why requires 5 DC amps per each AC amp?

              April 4, 2013 a 7:11 am
              • Amperage is the flow of electricity, while voltage is the pressure. Saying that it requires 5amps DC to 1 amp AC is not a correct statement. What is true is that in a 13volt (12 volt nominal) DC system, ran through an inverter that is about 80% efficient, the total power useage is approximently 78 watts, which would be a little under 1 amp at 115VAC. Wattage is the total power, which is comprised of voltage * amperage. If you change the voltage, but leave the wattage (total power) the same, then the amperage has to change as well.

                Jeremy Fear
                April 4, 2013 a 9:21 am
              • Ok I used your tool above (THANK YOU SO MUCH FOR THIS TOOL) to determine the battery I will require to run my 5V 2A device from a 12volt battery. The tool returned .92amp DC. So my question is how can I now determine what size battery in amp hours I require to run this device for 10 hours?

                April 11, 2013 a 9:05 am

                  Jeremy Fear
                  April 12, 2013 a 7:49 am
                • Would this calculator also work if I wanted to know what a switch that was rated AC would handle in DC?

                  June 17, 2013 a 11:36 am
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