Amp-hours describe charge
An Ah rating is useful for batteries at the same voltage, but it is not a complete energy figure by itself. Voltage is required before two different battery systems can be compared fairly.
Battery energy conversion tool
Battery Ah to Wh Calculator
The Battery Ah to Wh Calculator converts battery capacity in amp-hours and nominal voltage into watt-hours and kilowatt-hours. Enter the Ah rating and voltage from a battery label or datasheet to compare stored energy across 12V, 24V, 48V, LiFePO4, lithium-ion, lead-acid, RV, solar, marine, and backup-power systems.
The core relationship is simple: watt-hours equal amp-hours multiplied by volts. The calculator keeps that conversion separate from depth of discharge, inverter efficiency, runtime, charging limits, and wiring requirements so you can see exactly what the number means.
Because the Battery Ah to Wh Calculator is a unit-conversion tool, it is useful at the beginning of a battery-planning workflow. You can first translate a familiar Ah label into Wh, then decide whether you need a separate runtime, usable-capacity, charging, or wiring calculation. That separation makes it easier to spot where an assumption entered the process and prevents one convenient number from being mistaken for a complete system design.
Battery Ah to Wh Calculator conversion tool
Enter two positive values. The tool calculates nominal battery energy without silently adding discharge reserves, losses, or runtime assumptions.
Convert amp-hours and voltage to battery energy
Use the battery bank's rated Ah and nominal DC voltage. Decimal values are supported, and the presets provide quick checks for common battery classes.
Nominal battery energy result
Watt-hours
Kilowatt-hours
Reverse check
100 Ah × 12.8 V = 1,280 Wh of nominal battery energy.
Voltage completes the conversion
A 100Ah battery at 12.8V represents twice the nominal energy of a 100Ah battery at 6.4V. The Battery Ah to Wh Calculator makes that voltage effect visible immediately.
Watt-hours describe energy
Wh is often the clearer number for comparing batteries at different voltages. For broader unit conversions, use the Battery Capacity Calculator.
How to use the Battery Ah to Wh Calculator correctly
Start with nameplate values, keep nominal energy separate from usable energy, and choose the next calculator only after you know what question you are actually trying to answer.
The Battery Ah to Wh Calculator uses one transparent equation: Wh = Ah × V. If a battery is rated 100Ah at 12.8V, the nominal energy is 1,280Wh. If a different battery is rated 100Ah at 25.6V, its nominal energy is 2,560Wh. The Ah numbers are identical, but the second battery stores twice the nominal energy because its voltage is twice as high.
This distinction is why watt-hours are so useful when comparing systems. A battery listing that only emphasizes Ah can be misleading when the voltages differ. If you already know watt-hours and need to calculate capacity in the opposite direction, use the Wh to Ah Calculator. If you need watts multiplied by operating time, the Watt Hour Calculator handles that broader energy calculation.
The Battery Ah to Wh Calculator is also useful when specifications are written in different units. One manufacturer may advertise a battery as 200Ah while another emphasizes 2.56kWh. Once you know that the 200Ah battery is rated 12.8V, the conversion gives the same 2.56kWh figure. Converting both products to a common energy unit makes the comparison more meaningful, although you should still compare usable capacity, current limits, warranty conditions, cycle-life claims, and operating temperature separately.
Read the battery label
Use the rated capacity for the complete battery or bank and the nominal DC voltage stated by the manufacturer. Do not substitute charger voltage or AC inverter output voltage.
Compare lithium voltage rangesConvert to nominal Wh
Multiply Ah by V. That number is a nominal energy reference, useful for comparing battery sizes and checking product specifications at the same reference conditions.
Check LiFePO4-specific planningAdd real-world assumptions later
Runtime, usable depth of discharge, inverter loss, battery age, temperature, and load behavior are separate questions. Keep the base conversion clean, then model those effects with the right tool.
Estimate battery runtimeBattery Ah to Wh Calculator formula and assumptions
The conversion is exact for the numerical inputs you provide. The practical accuracy depends on whether those inputs describe the battery correctly.
Watt-hours (Wh) = Amp-hours (Ah) × Nominal voltage (V)
For a 100Ah battery at 12.8V, the calculation is 100 × 12.8 = 1,280Wh, or 1.28kWh. Reversing the equation gives Ah = Wh ÷ V, so 1,280Wh ÷ 12.8V returns 100Ah. The calculator shows this reverse check as a quick way to verify the arithmetic.
The unit relationship is consistent with standard electrical definitions. NIST lists one ampere-hour as 3,600 coulombs and one watt-hour as 3,600 joules in its Guide to the SI conversion factors. In practical battery work, multiplying the charge rating in Ah by the relevant voltage gives the corresponding energy in Wh.
Use nominal voltage for a nameplate-style energy conversion unless the manufacturer specifies another basis. Battery terminal voltage changes during charging and discharging, so a random meter reading is not a stable substitute for the rated nominal voltage. For example, Victron lists 12.8V 100Ah and 25.6V 100Ah LiFePO4 models with nominal energies of 1,280Wh and 2,560Wh in its official Lithium Battery Smart technical data.
That example also shows why the Battery Ah to Wh Calculator should not automatically round every “12V” battery to exactly 12.0V. Marketing classes and nominal pack voltages are related but not always identical. Entering the datasheet value preserves the manufacturer's stated energy relationship. When only a broad system class is known, a 12V, 24V, or 48V estimate can still be useful for early planning, but it should be replaced with the exact nominal voltage before purchase or detailed design decisions.
Nominal voltage matters
A LiFePO4 battery sold for a 12V-class system may be rated 12.8V nominal. Using 12V produces 1,200Wh for 100Ah; using 12.8V produces 1,280Wh. Use the exact product rating when precision matters.
Plan a 12V lithium systemReverse conversion is simple
If a portable power station or battery is labeled in Wh, divide Wh by battery voltage to estimate Ah at that voltage. Do not divide by the inverter's AC output voltage.
Reverse Wh back to AhConvert mAh before using Ah
For small packs, divide milliamp-hours by 1,000 to get amp-hours. A 20,000mAh pack is 20Ah. You can also skip that extra step with the dedicated mAh conversion tool.
Convert mAh directly to Wh7 Battery Ah to Wh Calculator examples
These worked examples show why the same Ah rating can represent very different energy at different voltages.
Each example below uses nominal voltage and the same basic equation. The results do not automatically represent usable energy at the load. If you intend to preserve a discharge reserve, apply that reserve after the nominal conversion. The Battery Depth of Discharge Calculator can help with that next step.
| Example | Capacity | Voltage | Calculation | Nominal energy |
|---|---|---|---|---|
| Small LFP cell | 20Ah | 3.2V | 20 × 3.2 | 64Wh |
| Small 12V battery | 10Ah | 12V | 10 × 12 | 120Wh |
| 12.8V LiFePO4 battery | 50Ah | 12.8V | 50 × 12.8 | 640Wh |
| 12.8V LiFePO4 battery | 100Ah | 12.8V | 100 × 12.8 | 1,280Wh |
| Nominal 24V battery | 100Ah | 24V | 100 × 24 | 2,400Wh |
| 25.6V LiFePO4 battery | 100Ah | 25.6V | 100 × 25.6 | 2,560Wh |
| Nominal 48V battery | 100Ah | 48V | 100 × 48 | 4,800Wh |
A 51.2V 100Ah battery would be 5,120Wh. The table uses 48V for the seventh example to show the difference between a broad system class and a chemistry-specific nominal pack voltage.
The Battery Ah to Wh Calculator can be checked manually against every row. Multiply the Ah value by the listed voltage and the result should match the Wh column. This simple verification is useful when reviewing product listings, comparing an older lead-acid bank with a lithium replacement, or checking whether a seller has mixed up Ah and Wh. If a quoted energy figure differs materially from the direct multiplication, look for the stated nominal voltage, test conditions, or whether the figure describes usable rather than nominal energy.
Why 100Ah is not a universal energy size
Compare the fourth, sixth, and seventh rows. All three batteries are 100Ah, yet they represent 1,280Wh, 2,560Wh, and 4,800Wh. A buyer comparing only Ah would miss a large difference in stored energy. This is the main reason the Battery Ah to Wh Calculator asks for voltage every time.
Once batteries are converted to Wh or kWh, comparing storage sizes becomes much easier. For a more complete sizing workflow that includes loads and reserve margins, use the Battery Sizing Calculator.
Nominal energy versus delivered energy
A 1,280Wh nameplate calculation does not guarantee 1,280Wh at an AC outlet. Depth of discharge, conversion losses, temperature, battery age, BMS cutoffs, wiring losses, and load behavior can reduce delivered energy. The nominal conversion is still useful because it provides a clear starting reference.
If your next question is how long the battery will power an appliance, use a runtime model with realistic load watts and losses rather than treating Wh as guaranteed operating time.
Using the Battery Ah to Wh Calculator for battery banks
Series and parallel wiring change bank ratings differently. Calculate the bank voltage and bank Ah first, then convert the completed bank to watt-hours.
For compatible batteries in parallel, voltage stays the same while Ah adds. Two 12.8V 100Ah batteries in parallel form a 12.8V 200Ah bank, so the nominal energy is 200 × 12.8 = 2,560Wh. For compatible batteries in series, voltage adds while Ah stays the same. Two 12V 100Ah batteries in series form a 24V 100Ah bank, also equal to 2,400Wh.
The total nominal energy increases when another equal battery is added in either valid arrangement, but you must enter the resulting bank ratings correctly. Do not add Ah in series or add voltage in parallel. The Series / Parallel Battery Calculator can help verify the configuration before you use the Battery Ah to Wh Calculator.
For mixed or expandable systems, calculate from the finished bank rather than multiplying labels casually. The Battery Ah to Wh Calculator assumes the bank rating you enter is electrically valid. Batteries with different capacities, chemistries, ages, BMS designs, or states of charge may not be suitable to combine. Manufacturer instructions take priority over generic series-and-parallel arithmetic, especially when a product limits the number of packs that may be connected together.
Parallel example
2 × 12.8V 100Ah in parallel
Bank rating: 12.8V, 200Ah. Nominal energy: 2,560Wh. Capacity in Ah doubles while voltage remains unchanged.
Series example
2 × 12V 100Ah in series
Bank rating: 24V, 100Ah. Nominal energy: 2,400Wh. Voltage doubles while Ah remains unchanged.
Compatibility comes first
Only combine batteries when the manufacturer permits the intended series or parallel arrangement. Match product requirements, state of charge, cabling, protection, and BMS rules before treating batteries as one bank.
Battery Ah to Wh Calculator accuracy, limits, and safety notes
The arithmetic is straightforward, but battery systems are not. Keep the conversion in its proper role and verify product-specific limits before making installation decisions.
What the result includes
- Rated battery capacity in amp-hours.
- The nominal battery-side voltage you enter.
- Nominal watt-hours and kilowatt-hours.
- A reverse Ah check using the same voltage.
For those inputs, the Battery Ah to Wh Calculator performs direct unit arithmetic. Decimal values work normally, so 37.5Ah at 12.8V returns 480Wh.
What the result does not include
- Depth-of-discharge reserve or state of charge.
- Inverter, converter, cable, or standby losses.
- Temperature, aging, discharge-rate, or cell-balance effects.
- BMS current limits, surge limits, fuse size, or cable gauge.
Use the Battery State of Charge Calculator when remaining charge is the actual question, and use the Wire Gauge Calculator for conductor planning.
The Battery Ah to Wh Calculator is therefore best treated as the first clean conversion in a chain of decisions, not as the final answer to every battery question. A correct Wh result can still sit inside an unsafe design if current, charging, protection, temperature, enclosure, or installation requirements are ignored.
Do not use inverter output voltage
A 12V battery feeding a 120V or 230V inverter is still a 12V-class battery on the DC side. To calculate battery Wh from battery Ah, use battery-side nominal voltage. Using AC output voltage would produce a meaningless battery-energy figure.
Do not treat Wh as a current rating
A battery can have enough stored energy for a task yet still be unable to supply the required current safely. BMS limits, cable ampacity, fuse ratings, connector limits, surge current, and voltage drop must be checked independently.
Practical accuracy note: use the exact rated Ah and nominal voltage from the battery or bank datasheet whenever the decision matters. A nameplate conversion is useful for comparison and planning, but it does not replace manufacturer specifications, applicable electrical requirements, or qualified installation guidance for high-current systems.
Battery Ah to Wh Calculator frequently asked questions
These answers cover the most common conversion mistakes, voltage choices, battery-bank questions, and next-step calculations.
Multiply amp-hours by nominal battery voltage: Wh = Ah × V. A 100Ah battery at 12V equals 1,200Wh, while a 100Ah battery at 12.8V equals 1,280Wh. The Battery Ah to Wh Calculator performs this conversion and also shows kWh.
Amp-hours measure charge, not energy by themselves. Voltage determines how much energy that charge represents. The same 100Ah rating can equal 1,280Wh at 12.8V or 2,560Wh at 25.6V.
Use the nominal voltage printed on the exact battery or listed in its datasheet. Many LiFePO4 products used in 12V-class systems are rated 12.8V nominal, but the product specification should control your input.
No. At 12V, 100Ah is 1,200Wh. At 24V it is 2,400Wh, and at 48V it is 4,800Wh. This is why comparing battery Ah without also comparing voltage can be misleading.
No. It intentionally returns nominal energy from Ah and voltage only. If you plan to use 80% or 90% of nominal energy, apply that chosen usable fraction afterward and follow the battery manufacturer's guidance.
No. Conversion losses affect energy delivered to a load, not the basic nominal Ah-to-Wh relationship. For runtime, use a separate model that includes realistic efficiency and average load power.
Yes, after you determine the correct bank rating. In parallel, compatible battery Ah adds while voltage stays the same. In series, voltage adds while Ah stays the same. Confirm the manufacturer's connection rules before combining batteries.
Divide watt-hours by voltage: Ah = Wh ÷ V. For example, 1,280Wh ÷ 12.8V = 100Ah. Use the site's Wh to Ah Calculator when the reverse conversion is your main task.
Related battery calculators and guides
Move from a clean Ah-to-Wh conversion to the next calculation only when you need the extra assumptions. The Battery Ah to Wh Calculator establishes the nominal energy reference; these related tools help answer different questions without mixing their assumptions into the base conversion.
Wh to Ah Calculator
Reverse the conversion when energy in watt-hours and battery voltage are already known.
Use reverse converterBattery Runtime Calculator
Estimate operating time from battery energy, load power, usable capacity, and practical loss assumptions.
Estimate runtimeSeries / Parallel Calculator
Determine how battery-bank voltage and Ah change before converting the final bank rating to Wh.
Check bank configurationConvert battery capacity before planning runtime or system size
Use the Battery Ah to Wh Calculator to establish nominal energy first. Then compare that result with your usable-capacity plan, load profile, charging method, BMS limits, and wiring requirements before making equipment decisions.
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