Ah to Watts Conversion Calculator

Enter amp-hours or watts into the calculator to convert to the other value using your specified voltage and time.

Common Mistakes Quick tips

Entering values in both fields. Fill exactly one: either Amp-hours or Watts.
Leaving out voltage or time; both are required to relate Ah and W.
Confusing Watts (W) with watt-hours (Wh), or Amp-hours (Ah) with amps (A).
Mixing mAh and Ah without converting (1 Ah = 1000 mAh).
Assuming peak power instead of average power; this conversion gives average power over the specified time and assumes roughly constant voltage.

When to Use This Calculator

Estimating average load (W) a battery can supply over a target runtime.
Finding required battery capacity (Ah) for a device with known power draw and runtime.
Converting between energy (Wh), capacity (Ah), and power (W) using the battery’s voltage.

Input Definitions

Voltage (V) — enter in V, kV, or mV.
Time (t) — duration in hours, minutes, seconds, or days (converted to hours).
Amp-hours (Ah) — battery capacity; mAh is supported (1 Ah = 1000 mAh).
Watts (W) — average power over the entered time.
Conversions — Wh = Ah × V; W = (Ah × V) ÷ t; Ah = (W × t) ÷ V.

Ah to Watts Formula

Use the following formulas to relate amp-hours, watts, voltage, and time; energy in watt-hours is simply capacity times voltage.

\quad \mathrm{W}=\frac{\mathrm{Ah}\cdot V}{t_{\mathrm{h}}}\quad\quad \mathrm{Ah}=\frac{\mathrm{W}\cdot t_{\mathrm{h}}}{V}

Watts (W) measure power; Watt-hours (Wh) measure energy: 1 Wh = 1 W for 1 hour.
Amp-hours (Ah) measure capacity; convert mAh to Ah by dividing by 1000.
These equations assume approximately constant voltage across the discharge period.

How do you convert Ah to Watts? Multiply amp-hours by voltage and divide by time in hours: W = (Ah × V) ÷ t.

How do you convert Watts to Ah? Multiply watts by time in hours and divide by voltage: Ah = (W × t) ÷ V.

Average Power from Capacity at 12 V and 24 V (t = 1 hour)
Amp-hours (Ah)	Watts @ 12 V	Watts @ 24 V
0.5	6	12
1	12	24
2	24	48
5	60	120
10	120	240
20	240	480
50	600	1200
100	1200	2400
* For t = 1 hour: W = Ah × V. For other times, use W = (Ah × V) ÷ t.

Convert 4.8 Ah at 20 V over 2 hours to watts.

Use the formula: W = (Ah × V) ÷ t.

W = (4.8 × 20) ÷ 2 = 48 W