Watt-hours and amp-hours are both units for electric charge.
1 watt-hour is defined as 1 watt of power expended for 1 hour.
1 amp hour is defined as 1 amp of current expended for 1 hour.
How do you convert watt-hours to amp-hours?
It is possible to convert watt-hours to amp-hours using the following formula:
Watt-hours = Amp-hours * Volts
To calculate amp-hours from watt-hours, we need to rearrange this equation to:
Amp-hours = Watt-hours / Volts
For the watt-hour to amp-hour conversion, you also need voltage (V).
Here is a nifty amp-hour calculator that converts watt-hours to amp-hours. Further on, you’ll also find a chart of Wh to Ah for 120V and 220V.
Wh To Ah Calculator
Watt-Hours To Amp-Hours Conversion Chart
| Watt-Hours (Wh) | Amp-Hours (at 120V): | Amp-Hours (at 220V): |
|---|---|---|
| 1 amp hour to watt hours: | 0.008 Ah | 0.005 Ah |
| 10 amp hours to watt hours: | 0.08 Ah | 0.05 Ah |
| 20 amp hours to watt hours: | 0.17 Ah | 0.09 Ah |
| 30 amp hours to watt hours: | 0.25 Ah | 0.14 Ah |
| 40 amp hours to watt hours: | 0.33 Ah | 0.18 Ah |
| 50 amp hours to watt hours: | 0.42 Ah | 0.23 Ah |
| 100 amp hours to watt hours: | 0.83 Ah | 0.45 Ah |
| 200 amp hours to watt hours: | 1.67 Ah | 0.91 Ah |
| 500 amp hours to watt hours: | 4.17 Ah | 2.27 Ah |
| 1000 amp hours to watt hours: | 8.33 Ah | 4.55 Ah |
You can also do the reverse conversion. To help you out, we have created a similar Ah to Wh converter here.
Note: Due to low battery capacity, it’s quite hard to produce battery-powered HVAC appliances such as air conditioners, furnaces, heaters, and so on. It might be interesting to read our articles about battery-operated heaters here and battery-powered air conditioners here.
if i have one appliance that draw 350 watts at 120 volts and i use a 100 amp hour lutetium battery will it last me 34 hour if drained 100% or am i figuring something wrong
Hello William, that appliance draws about 3 amps (350W/120V = 2.9 amps). 100 amp hours battery will supply 1 amp of electrical current for 100 hours. Or, as in your case, it will provide 3 amps for about 34 hours. That’s the basic logic. That does presume that your voltage is 120V; however, most batteries have 12V voltage. That will increase the electrical current you need to use to generate 350W by 10. That means that draw will be 30 amps; and the battery will last only 3.4 hours.
Where did you get the 10? I have 200ah lifepo4 battery and 110w consume. How long will it drain the battery?
Hello Alfred, factor 10 comes from different voltages, 120V vs 12V, the ratio is 10. 200 Ah battery has lifepo4 4 cells with about 3V voltage each, bringing the total to 12V. 110W consumption is probably on 120V; it runs on 110W/120V = 0.92 amps. You calculate 200 Ah / 0.92 A = 217 h. The 110W device should drain the battery in about 217 hours.
Quick question, the 0.92 amps consumption is relevant to 120V – on the 12V battery, wouldn’t the consumption ramp up to 9.2A to generate 110W in this example? (Factor of 10 correction)
So wouldn’t the battery only last 21.7 hours rather than 217 hours?
If I have a small solar panel capable of 30w optimally, and a portable fridge that operates at an average 0.89ah/Hr @12v that works out to 0.89×12= 10.86 w/hr, does that mean the 30w panel could operate the fridge without assistance from an external battery source, given the panel is in direct sunlight conditions for the hours needed to operate in the day time? If so, then even at half solar output (15w) it would still manage to operate the fridge? Thanks
Hello John, your calculations are on point. If your solar panel can provide 30W of power, it will run a 10.86W fridge. Even at the half output, it should be enough.
I am looking at electric bicycles. One bike I’m looking at has a 960wh battery and a 1200watt motor, and the other one has a 52v 19.2ah battery and a 1000watt motor. I can’t tell which one is better. Help!
Hello Jasmine, an interesting question. So, the key here is to calculate the battery of the second bike. You have to multiply 52V and 19.2ah and you get 998.4wh. The first bike has a more powerful motor but shorter battery life. The second bike has a less powerful motor but a better battery life. Hope this helps.
Hello, I’m looking at buying the ICECO VL60 dual Frig and Freezer that draws 45w and I have a 300w of solar panels to a 100AH Lithium Iron smart battery. The only other draw is from 3w LED lights and a 3w fan for my composting toilet. Can my system handle the ICEO? Thanks
Andy
Hello Andrew, if your solar panels continually provide 300 watts of power, you can it can easily handle 45W + 3W + 3W = 51W of power draw. Of course, the problem is that solar panels don’t continually provide 300W.
Let’s say that power flow drops to 0W during the night. For how long can the 100 Ah battery provide power to appliances with the combined wattage of 51W? Well, 100 Ah battery probably has 12V voltage; that means that at full capacity, the battery stores 1,200 Wh. 1,200 Wh / 51W = 23,5 hours. That 100 Ah battery can provide power to the whole system (freezer + LED lights + fan) for about 24h.
All in all, the system can handle the new freezer. Hope this helps.
Hello, in this case, you have to know, that you must not discharge battrery mor than 50%. Now you have only 12 hour to use.
Hello,
Could I ask a question please? I have two leisure batteries that each have 95amp/h or 1140 watt hours.
I have a cool box, in the information leaflet it details the consumption as 55w on 12v. Does that mean 55w per hour? I can’t find anything to indicate an hourly rate.
If so then does that mean that I could run that cool box for just over 41 hours?
Thank you.
Trish
Hello Trish, two batteries combined have a capacity of 2280 Wh (at 12V). The cool box runs on 55 Watts; it will drain 55 Wh (every hour). That means that the cool box will run for 2280 Wh / 55 W = 41.5 hours; as you have correctly calculated, well done!
Convert 338 w to Ah
Hello Bassey, for every conversion, you also need voltage. Let’s say you have a standard 12V battery that produces 338W output. That means the battery generates 338W / 12V = 28.2 amps. That would mean that 338 Wh is equal to 28.2 Ah. Hope this helps.
How many batterys do I need to run 1000w for 5 hours
What size battery
How many amp
And for 3000w
Hello Bailey, 1000W for 5 hours is equal to 5 kWh. Batteries have 12V voltage; in this case, you would need a 416.67 Ah battery. Such a battery has an 83.3 amp output. For 3000W, you just multiply these numbers by 3 and you get the numbers.
Hi, I would like to ask the following
I’m looking to buy a power station for emergency power outage in the winter.
Specifically, I’m planning to use a 1500W room heater for 8hr in such setting, which I haven’t found one yet, but I did find a power station stating 1260Wh with some 120V 15amp outlets. I’m confused as it also said “AC inverter output: 1800W continuous.”
So would this power station good enough or I may need a bigger capacity one.
Hello Brooks, first you need to check if the output wattage is sufficient (at least 1,500W). The 120V 15amp output generates 120V*15A = 1,800W. This checks out, great. Now, 1,260 Wh means that such a power station can provide 1,260W wattage for 1 hour. You can power a 1,500W for about 50 minutes. So, not 8 hours. This is a very small power station; you would need a bigger one.
So interesting
Am very grateful for your explanation
hi im buying a beer bike and am looking to install a draft beer machine
its 1.5a 220v
the battery which comes with the bike is 60v – 80ah
the motor for the bike is 3500watts
my question is would I be able to run the machine and bike for roughly 6-8hrs or will I need to install another battery
thank kindly
ian
Hello Ian, cool gig. Let’s calculate a bit; the draft beer machine will run on 1.5A*220V = 330W (operating at 100% capacity). The battery has 60V*80Ah = 4,800 Wh capacity. With this, you can run the machine at 100% capacity for 14.5 hours, or a bike at 100% capacity for 1.37 hours. Now, the bike doesn’t operate at 100% capacity (3,500W) all the time; it operates at a significantly lower output. It’s very hard to say what the actual average draw will be. In order for the battery to last for let’s say 6 hours, the new wattage draw should be 800W. That’s 330W for the machine and 470W for the bike. These are the kind of calculations you can make but, in practice, the output is nearly impossible to figure out. Hope it helps a bit.
I have a 12ah 12V small cute battery:) it can support my table fan with 70watt 240V~50Hz how many hours?
Hello there. The small cute battery has a 144 Wh capacity. It will power your 70W table fan for a little over 2 hours.
I would like to know how long I can run a 1700w appliance connected to a 240v inverter on a 240ah lithium battery?
Thanks in advance
Hello Darren, the 1,700W appliance runs on 1,700W / 240V = 7.1 amps when running at 100% capacity. With a 240 Ah lithium battery, you can run it for 240Ah / 7.1A = 33.8 hours. Hope this helps.
Hi, I am trying to power a LCD screen using a portable power bank and would like to know what size battery I need to power if for 6 hours.
The screen runs at 130mA at 12V apparently, so 1,560 mW.
This equates to 1.56 Wh
So, 1.56Wh x 12V/1000 = 130 mAh per hour
=> 130 * 6 = 780 mAh
This doesn’t seem right. Can any help please?
Hello Alex, your calculations are on point. Both the LCD screen and the portable power bank run on 12V. If the screen draws 130 mA, you need a 130 mAh power bank to run it for 1 hour. If you want to run it for 6 hours, that’s a 780 mAh power bank. That LCD, as you have correctly calculated, really requires minimal input power; 1.56W. That’s why even a small power bank can run it for so long.
dude i just wanna say you’re awesome answering all these questions for people lol
Lol Nick, thanks a lot! 🙂
Yea man you have helped these people a lot. I read all of them. Not sure why because I am very familiar with the formulas. But props to you for being so kind. I hope your at least making money from the ads on this site ….
Hi if a car ref draws 1amp hour per hour. How long can my 12volt 500 wh power station run the fridge?
Hello Dondi, you have to first convert Wh to Ah. 500Wh at 12V is equal to 500Wh/12V= 41.7 Ah. That means that your power station can run the fridge for almost 42 hours. It’s important here to be aware of the start-up watts your fridge requires (it can be 3x or even 4x higher than running wattage). You can read a thing or two about how big a generator or power station you need to run a fridge here.
Thanks very much! You are an absolute superstar! You are amazing
Please convert 532.8wh 12V to ah and explain to me how many hours can it powered appliances of 80w in total on full charge?
Hello Sunday, have you tried using the calculator above? Here’s how you can do it manually: 532.8 Wh / 12V = 44.4 Ah. Alright, for an 80W appliance, you have to use watt-hours. Here’s how you do that: 532.8 Wh / 80 W = 6.66h. You will be able to run an 80W for a little less than 7 hours. Hope this helps.
I have a Northstar NSB12-730RT battery.
I was using your calculator and it seems my battery capacity is higher than I originally figured, can you check my math.
Battery states 731 watts per cell at 4C rate.
12v cell means 4386wh of power.
Converted to ah = 365.5AH at 4C??
I thought this was a 200-220AH battery.
Hello Jason, here’s how you can look at this. If a 12V battery states that it can produce 731W, that means it will generate 731W/12V = 61A of current while generating 731W. That’s not an indicator of battery capacity; it’s an indication of battery power output. The key difference (if you want to calculate capacity) is how long can a battery sustain this power output.
Now, if you check the Northstar NSB12-730RT battery specs, you can see, for example, that this battery can generate 279W of electricity for 1h (at 1.75V discharge). That means that the battery contains 279Wh worth of electricity. How many Ah is that? Well, we have 1.75V voltage from the specs, so 279Wh / 1.75V = 160Ah. That means that you don’t have a 200-220Ah battery; you have a 160 Ah battery.
I hope this makes sense, if not, just comment away and we’ll try to explain a bit more in-depth how all of these calculations work.
I have a 12VCD motor at 30W which will run at 50RPM’s and a torque of 6N.m (just in case this info will help). Most of the time, I will run it for an hour. However, I do want the capability to run it for 8 hours continuously. What battery should I consider?
Hello there, thanks for sharing all the info. To calculate the battery size you only need the wattage (30W) for Wh sizing and voltage (12V) for Ah sizing. Basically, if you want any 30W motor to run for 8 hours, you need 30W * 8h = 240 Wh battery. Now, battery capacity is, in most cases, expressed in amp-hours (Ah). Here’s how you calculate amp-hours: 240Wh / 12V = 20 Ah.
You would require a 20Ah 12V battery, or larger. Hope this helps.
I have a 60w flood light at 240v. Would this work on a 150w 240v inverter on a 18v 5ah battery
Hello Matt, it would work; but for how long? That’s usually the question. The battery has a capacity of 18V*5Ah = 90Wh. The flood light draws 60Wh per hour, which means that it will run for 1.5 hours on this battery.
Hello i am thinking about purchasing a 578Wh portable battery to trickle charge my car (battery) when not in use. I’m told that the car utilizes 50mA when parked. How can i calculate how long the portable battery will last?
Hello Joe, you have all you need to calculate that, presuming the car battery is 12V. Here’s how you can calculate that: Every hour, your car battery will draw 12V*0.05A=0.6Wh. That’s 0.6Wh per hour. You have a 578Wh battery. You calculate 578Wh/0.6Wh = 963.3 hours; that’s about 40 days (how long will the battery last). Hope this helps.