Watt-Hours Measure Energy
Wh tells you how much electrical energy is stored or consumed. Because it already includes voltage, watt-hours are useful for comparing battery packs that operate at different voltages.
Explore watt-hoursWh to Ah Calculator
Use this Wh to Ah Calculator to convert watt-hours into amp-hours at any battery or DC system voltage. Enter the energy in Wh and the relevant voltage, and the calculator applies the standard relationship Ah = Wh ÷ V instantly.
It is useful for comparing 12V, 24V, and 48V battery banks, translating energy requirements into battery capacity, and checking solar, RV, marine, backup, and portable-power plans before moving to detailed sizing.
Convert Wh to Ah Instantly
Enter watt-hours and voltage to calculate amp-hours. The result is a nominal electrical conversion, so it is ideal for unit comparison and early battery planning.
Watt-Hours to Amp-Hours Converter
Formula: Ah = Wh ÷ V. Use the voltage tied to the energy rating you are converting.
Converted Capacity
100 Ah
Equivalent mAh100,000 mAh
Input Energy1.2 kWh
Same Wh at 24V50 Ah
Same Wh at 48V25 Ah
1200 Wh ÷ 12 V = 100 Ah
Accuracy note: this conversion does not automatically include inverter loss, depth of discharge, temperature effects, battery aging, voltage sag, or BMS limits. For real system sizing, apply those factors separately.
The Wh to Ah Calculator is most useful when you know an energy requirement in watt-hours but battery products are labeled in amp-hours. For example, if a planned load needs 1,200Wh and you are comparing a 12V battery bank, the nominal conversion is 1,200 ÷ 12 = 100Ah. At 24V, the same 1,200Wh corresponds to 50Ah, and at 48V it corresponds to 25Ah.
That difference is why voltage must be part of the conversion. Amp-hours alone do not tell you the total energy in a battery. If you want to reverse the calculation, use the Battery Ah to Wh Calculator. For a wider set of Ah, Wh, mAh, and runtime conversions, the Battery Capacity Calculator is the better all-in-one tool.
Read the Wh to Ah Calculator result as a voltage-specific capacity equivalent. A result of 100Ah does not mean every 100Ah battery stores the same energy, because a 100Ah battery at 12V contains far less nominal energy than a 100Ah battery at 48V. That distinction becomes especially important when comparing product listings, combining batteries into a bank, or translating a load estimate into a purchase specification.
For planning, keep the conversion step separate from the sizing step. First use the Wh to Ah Calculator to translate units. Then decide how much reserve, usable depth of discharge, conversion efficiency, temperature margin, and future expansion your application needs. This two-step approach makes the assumptions visible and reduces the risk of treating a mathematically correct conversion as a complete electrical design.
Wh to Ah Calculator Guide
Use the table of contents to jump from the conversion formula to voltage selection, worked examples, real battery sizing, limitations, and FAQs.
How Wh to Ah Conversion Works
Watt-hours measure energy, amp-hours measure charge, and voltage connects the two. The Wh to Ah Calculator simply rearranges the standard battery energy relationship.
The base relationship is Wh = Ah × V. If watt-hours and voltage are already known, divide both sides by voltage to get Ah = Wh ÷ V. The U.S. Federal Aviation Administration uses the same relationship when explaining how to determine lithium-battery watt-hour ratings from amp-hours and voltage. Its passenger battery guidance states that watt-hours are found by multiplying volts by amp-hours, which is the same equation rearranged for this calculator.
Amp-hours (Ah) = Watt-hours (Wh) ÷ Voltage (V)Suppose you have a 1,280Wh energy rating at 12.8V. Dividing 1,280 by 12.8 gives 100Ah. If you instead divide 1,280Wh by 25.6V, the answer is 50Ah. Nothing happened to the amount of energy; only the voltage basis changed. This is why a valid Wh-to-Ah conversion always needs a voltage value.
For a broader explanation of watt-hours themselves, see the Watt Hour Calculator. If your starting value is in milliamp-hours rather than watt-hours, use the mAh to Wh Calculator first, or use the Wh to mAh Calculator when you need the smaller charge unit used on phones, power banks, and electronics.
Amp-Hours Measure Charge
Ah tells you how much electric charge a battery can deliver. It is meaningful for energy comparison only when you also know the voltage associated with that Ah rating.
Compare capacity unitsVoltage Links Wh and Ah
Higher voltage means fewer amp-hours for the same watt-hours. That is why 4,800Wh can be 400Ah at 12V, 200Ah at 24V, or 100Ah at 48V.
Review lithium voltagesWhy Voltage Matters in a Wh to Ah Calculator
Choosing the right voltage is the most important input after the watt-hour value because the same energy target produces a different Ah result at every voltage.
For a battery label or battery-bank comparison, use the nominal voltage tied to that battery rating. A battery marketed as “12V” may use a nominal value such as 12.8V for a LiFePO4 pack, while a 24V-class LiFePO4 pack may be specified at 25.6V. Victron, for example, lists Lithium Battery Smart products at 12.8V and 25.6V nominal. That does not mean every lithium battery uses those exact values, so always use the manufacturer value for the product you are evaluating.
Measured terminal voltage is not automatically the right input for capacity comparison. Real battery voltage changes with state of charge, load, temperature, and chemistry. Nominal voltage gives a consistent reference for rated energy math. If you intentionally want a conversion at a measured operating point, you can enter that measured voltage, but interpret the result as a calculation at that specific voltage rather than as a universal battery capacity rating.
Nominal Voltage vs. Live Voltage
Nominal voltage is a standardized reference used to describe a battery or system. Live terminal voltage can rise and fall during charging and discharging. For nameplate conversion, nominal voltage is usually the more consistent choice.
If you are working with LiFePO4 systems, the dedicated LiFePO4 Battery Calculator can help you move from simple unit conversion into usable-energy and runtime planning.
12V, 24V, and 48V Systems
System labels are convenient categories, but the exact nominal voltage depends on battery chemistry and pack design. Use the product datasheet when precision matters, then compare with the site's 12V, 24V, or 48V lithium battery calculators for voltage-specific planning.
Using Wh to Ah Calculator Results for Battery Sizing
A Wh-to-Ah result is a conversion, not a final battery recommendation. Good sizing starts with the converted Ah and then applies the real operating assumptions of the system.
1. Decide Whether Wh Is Rated or Required Energy
If the Wh value came from a battery label, the calculator translates that nameplate energy into Ah at the selected voltage. If the Wh value came from your appliances, it may represent energy that must reach the load rather than energy that must be stored in the battery. Those are not always identical because conversion losses can exist.
For a load-based plan, the Battery Sizing Calculator helps move beyond unit conversion into a capacity estimate based on expected use.
2. Apply a Usable-Capacity Assumption
The Wh to Ah Calculator divides energy by voltage only. It does not reduce capacity for a planned reserve or depth-of-discharge limit. If your system should not use all nominal capacity, the battery's rated Ah will need to be higher than the direct converted Ah required at the load.
Do not assume one depth-of-discharge percentage fits every chemistry or product. Follow the battery manufacturer's recommendations and warranty conditions.
3. Include Conversion and Standby Losses
An AC load powered through an inverter can require more battery-side energy than the appliance's ideal Wh calculation because the inverter is not perfectly efficient and may also consume standby power. DC converters, wiring, and other electronics can add smaller losses.
For charging planning after selecting a battery size, use the Battery Charge Time Calculator.
4. Check Current, Wiring, and Protection
A correct Ah figure does not prove that a battery, BMS, fuse, cable, connector, or inverter can safely deliver the required current. High-power loads can exceed current limits long before the battery runs out of energy.
Use the site's Wire Gauge Calculator as an early conductor check, then verify the complete installation against equipment instructions and applicable electrical standards.
Wh to Ah Calculator Accuracy, Limitations, and Safety Notes
The Wh to Ah Calculator gives exact arithmetic for the values entered, but the quality of a battery plan depends on whether those values describe the real system correctly.
The equation itself is straightforward: divide Wh by V. The uncertainty enters when a voltage, energy figure, or system boundary is chosen incorrectly. A 1,200Wh battery divided by 12V equals 100Ah, while the same 1,200Wh divided by 12.8V equals 93.75Ah. Neither answer is inherently wrong; they describe different voltage assumptions. For product comparison, use the nominal voltage associated with the product's rating.
Battery chemistry also affects how much of a rated capacity is practical in service. Temperature, aging, discharge current, BMS cutoffs, charger behavior, and inverter efficiency can change the energy that is actually available. This page therefore keeps the conversion clean rather than hiding extra assumptions inside the result. For chemistry-specific context, review the Lithium Battery Safety Guide and relevant manufacturer documentation.
Temperature and Battery Age
Available capacity can shift with temperature and battery condition. A simple Wh-to-Ah conversion does not predict those changes, so critical backup designs should include appropriate reserve and be verified under expected conditions.
BMS and Current Limits
A battery may have enough energy on paper but still be unable to supply a high-current load. Confirm continuous and surge current limits for the battery, BMS, inverter, cables, fuses, and connectors.
Variable Loads and Efficiency
Real devices can cycle on and off, surge at startup, or draw different power in different modes. Use measured or representative energy data when possible rather than assuming the nameplate watts run continuously.
Authoritative references: the FAA battery guidance explains the Wh = Ah × V relationship used for lithium-battery watt-hour ratings. For a manufacturer example of nominal LiFePO4 voltages and model-specific specifications, see Victron Lithium Battery Smart 12.8V & 25.6V. Always use the datasheet for the battery you actually own.
Wh to Ah Calculator Examples for Common Battery Voltages
These worked examples show how the exact same watt-hour target turns into different amp-hour requirements as voltage changes.
| Energy | Voltage | Calculation | Result | Typical planning context |
|---|---|---|---|---|
| 600Wh | 12V | 600 ÷ 12 | 50Ah | Small backup or portable battery bank |
| 1,200Wh | 12V | 1,200 ÷ 12 | 100Ah | Common 12V reference example |
| 1,280Wh | 12.8V | 1,280 ÷ 12.8 | 100Ah | Nominal LiFePO4 example |
| 2,400Wh | 24V | 2,400 ÷ 24 | 100Ah | Medium-voltage battery bank |
| 2,560Wh | 25.6V | 2,560 ÷ 25.6 | 100Ah | Nominal LiFePO4 example |
| 4,800Wh | 48V | 4,800 ÷ 48 | 100Ah | Larger inverter or solar system |
| 5,120Wh | 51.2V | 5,120 ÷ 51.2 | 100Ah | Nominal LiFePO4 example |
| 9,600Wh | 48V | 9,600 ÷ 48 | 200Ah | Larger storage target |
1,800Wh ÷ 12V = 150Ah
RV Energy Target
If an RV load plan totals 1,800Wh and the battery bank is based on 12V nominal math, the unit conversion is 150Ah. Real battery selection should then account for usable depth of discharge, inverter efficiency, surge load, charging availability, and reserve. The RV Lithium Battery Calculator is better for that next step.
4,800Wh ÷ 48V = 100Ah
Solar Storage Target
A 4.8kWh storage target equals 4,800Wh. At a 48V reference, that converts to 100Ah. Solar design still needs autonomy days, charging energy, array production, inverter efficiency, and battery reserve, so continue with the Solar Battery Calculator instead of treating 100Ah as a complete system recommendation.
960Wh ÷ 24V = 40Ah
Backup Power Example
If a backup requirement is 960Wh at 24V, the direct conversion is 40Ah. That tells you the nominal charge capacity corresponding to the energy target. To estimate how long a battery can support an actual device load, move to the Battery Runtime Calculator.
Wh to Ah Calculator Frequently Asked Questions
These answers cover the most common questions about using a Wh to Ah Calculator for battery capacity, voltage comparison, and system planning.
The formula is Ah = Wh ÷ V. Divide watt-hours by the battery or system voltage that applies to the energy value. For example, 1,200Wh ÷ 12V = 100Ah.
No. Watt-hours measure energy and amp-hours measure charge, so voltage is required to connect them. A single Wh value can produce many different Ah values depending on voltage.
1,200Wh at 12V is 100Ah because 1,200 ÷ 12 = 100. At 12.8V, however, 1,200Wh is 93.75Ah, which shows why the voltage basis matters.
2,400Wh at 24V is 100Ah. If the battery bank's nominal voltage is 25.6V instead, 2,400Wh converts to 93.75Ah.
4,800Wh at 48V equals 100Ah. The same 4,800Wh would equal 400Ah at 12V or 200Ah at 24V.
For comparing rated battery capacity, use the nominal voltage associated with the product or battery bank. Use measured voltage only when you intentionally want a conversion at that specific operating point.
No. This page performs a direct unit conversion only. Apply inverter loss, usable depth of discharge, reserve, temperature, and other design factors separately when selecting a real battery bank.
Yes. The electrical unit relationship works across battery chemistries. What changes is the correct nominal voltage, usable capacity, operating limits, and other product-specific assumptions.
Wh is usually better for comparing total stored energy across batteries with different voltages because it already includes voltage. Ah is especially useful once you are working within a known system voltage.
No. Runtime also depends on load power, usable energy, efficiency, temperature, and battery condition. Use the Battery Runtime Calculator when time under load is the question you need to answer.
Use the Wh to Ah Calculator With Confidence
Use the Wh to Ah Calculator for the clean unit conversion, then pair the result with the site's sizing, runtime, charging, wiring, and safety guides so the final battery system reflects real operating limits rather than arithmetic alone.
Calculate Another Value