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.

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44 Responses,   4.5 Rating

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  • i have a 5000 watt invertor fitted to my nissan patrol ute .
    so how many 12volt batteries would i need to get max 240 volt power out of the invertor ???????

    Steve Southen
    June 30, 2016 a 5:01 am
    • As you can see by the calculator that would draw about 460 Amps an hour out of a 12v battery pack! Next I would suggest using our Calculator | Sizing a 12 Volt Battery to a Load, as it depends on how long you want to run that load for…

      BatteryStuff Tech
      January 19, 2017 a 10:28 am
    • pls I have a DC appliances that’s uses -48v and the current in my region is an AC with 200v – 220v, how do I get an accurate result?

      Ogboi Stephenson
      July 4, 2016 a 1:59 am
      • If your device runs off 48 volts then there is no need to be looking for an inverter. Your device is meant to run off either a 48v power-supply, or a 48v battery pack.

        BatteryStuff Tech
        January 25, 2017 a 7:19 am
      • It is hot in Houston. I have a 2000 Btu air conditioning with a power consumption of 270 watts and a nominal current of 2.9A plus a starting current at 13.9A while attempting to use 12vdc battery. What wattage inverter do I need? And how long do you think a car battery will last using the above setup?

        July 4, 2016 a 6:38 am
        • At 120VAC @ 2.9 amps your are drawing approximately 32 Amps a hour out of a battery. You would be lucky if a car battery could take that draw for even an hour before excessively discharging the battery. I would use our Calculator | Sizing a 12 Volt Battery to a Load, and just be sure to put in the DC amp draw of 32 Amps, and not the AC amp draw. As far as what inverter to purchase… You need to account for your surge draw which you state is 13.9 amps… 120VAC x 13.9 Amps = 1,668 Watts! The inverter you select must be able to handle that draw, and you might want to talk to the manufacturer to see how long that surge lasts. Most inverters come with a surge rating for less than a second, so if your surge last longer it generally forces you into a larger inverter.

          BatteryStuff Tech
          January 25, 2017 a 7:50 am
        • 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.

            BatteryStuff Tech
            October 31, 2012 a 3:09 pm
            • Very useful. But I believe Watts = Volts x Amps is Watts law. Not Ohms law.

              May 19, 2014 a 2:12 pm
              • Dave, that is correct. Thanks for the correction. Ohm’s law is V=I*R, Watt’s law is W=V*I, where V=voltage, I= current, R= Resistance, W= Wattage.

                BatteryStuff Tech
                May 21, 2014 a 12:48 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.

                RAJAVARDHANA NAIDU.G
                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
                        • Jordan, this calculator is a simple AC to DC conversion. It will not work for your situation. Thanks

                          BatteryStuff Tech
                          May 21, 2014 a 12:35 pm
                        • i wish to power a series of appliances whose total sum of wattage is 720 watts for a minimum of 3 hrs non stop. i have already purchased a 12v – 220v inverter which is rated 1500watts…my questions aer: what rating of one 12v battery (or a system of combined batteries) do i need to achieve this target.Also , what specification of solar panel charging system can charge the battery in a very short time like 2 hours of sunlight…we do have intense sunlight in my region.


                          May 26, 2014 a 6:41 am
                          • Please email your question to

                            May 27, 2014 a 9:45 am
                          • Hi tbere i am looking to no how long my 240 appliances will last for with 2 110 batteries working of a 1500watt inverter drawing 980watts in total a total of 88 odd amps of dc how long will my batteries last and what size of solar panel would suit to maintain my batteries as i have only a splitt relay wired as a charging system

                            Jonathan Burns
                            June 17, 2014 a 9:01 pm
                            • 240VAC doesn’t change the total power of the system. The same calculations will work. In your case, you will get roughly an hour 1/2 of run time.

                              BatteryStuff Tech
                              June 20, 2014 a 11:55 am
                            • I have a 24VDC power bay with a DC to DC convertor (-48VDC). If I’m reading 30amps on -48VDC side how much power is my 24VDC bay actually providing?

                              June 23, 2014 a 2:52 pm
                              • That depends on the efficiency of the converter. On the 48 volt side, you are using essentially 1450 watts. The wattage on the other side, the 24v side, will depend on the efficiency of the conversion process.

                                BatteryStuff Tech
                                June 25, 2014 a 9:05 am
                              • This is GREAT stuff.
                                Thank you ALL for the info.

                                Bill Mertz
                                August 12, 2014 a 10:07 pm
                                • Good morning.
                                  I have calculated that I need 300 Amps DC per day.
                                  How many 250 watt 12 volt solar panels do I need to keep up with this demand.
                                  My battery bank is 3000Ahs 12 volts.

                                  Bill Mertz
                                  August 13, 2014 a 11:30 am
                                  • Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

                                    August 15, 2014 a 2:25 pm
                                    • hi,
                                      why do we hav some devices taking negative voltage?
                                      e.g BTS operates in -48V (DC)

                                      August 21, 2014 a 5:14 am
                                      • Either the multi-meter is hooked up backwards, or you have forced the batteries to charge backwards. Usually you are reading the reverse terminals.

                                        BatteryStuff Tech
                                        August 22, 2014 a 9:45 am
                                        • Thanks, this was very helpful, but mainly to give me an idea of the current draw on the batteries so that I can work out what circuit breaker/fuse to get.

                                          August 26, 2014 a 4:13 am
                                          • Great tool.

                                            If you add inverter efficency as an optional input that might be good as well.

                                            September 6, 2014 a 4:51 am
                                            • Glad to help! I will send your recommendation up the food chain and see if we can make it happen!

                                              BatteryStuff Tech
                                              September 12, 2014 a 1:07 pm
                                            • I have a portable 5000 BTU air conditioner unit. The tag shows that it uses 504 watts and 4.5 to 4.8 Amps. It runs very well with a 1200 watt generator. How long can it run using an inverter, a 100 amp hour AGM battery rated at 1200 watts?

                                              September 11, 2014 a 9:19 am
                                              • 504 watts / 4.8 Amps = 105 VAC. This would pull 46.37 Amps DC, so you could run about an hour before you start to excessively discharge the battery.

                                                September 25, 2014 a 10:18 am
                                              • Can I use this in reverse? I have a 100A 240V sevvice but need to power a DC rectifier shelf that is capable of 200A. If I use this calculator and input 100A AC, 240VAC, 48VDC then the calculator shows 552A DC. DOes this mean that the 100A AC service can supply up to 552A DC?

                                                October 31, 2014 a 11:53 am
                                                • In reverse it would be a charger vs an inverter, however if the charger runs off 240VAC and draws a 100A then it will put out approximately 552A on a 48V system, but it might vary depending on the efficiency of the charger.

                                                  BatteryStuff Tech
                                                  November 19, 2014 a 10:23 am
                                                • amazing useful

                                                  May 4, 2016 a 1:50 am
                                                  • This tool was helpful. Just a quick question. I guilt a solar generator with a 100 watt panel, a 12V inverter that puts out 220 VAC and a 12 V battery. It is supposed to run a stock well that is 480 Amps. With just one battery it only runs 3 minutes the overloads the battery. If I read the calculator right this pump will draw 9715.20 Amps DC, but each 12 V battery will only put out 3,310 milliamps. So if I connect 3 12 V batteries in parallel, will that be sufficient to run this pump or should I connect 4 12 V Batteries?

                                                    April 20, 2016 a 9:19 pm
                                                    • Now that you used this calculator to determine what you will be drawing out of the battery. I would suggest using our Calculator | Sizing a 12 Volt Battery to a Load. This calculator will tell you what size battery pack you need to create depending on how long you want to run the well for.

                                                      BatteryStuff Tech
                                                      April 21, 2016 a 12:03 pm
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