Battery Life Calculator

Runtime from battery capacity and circuit current draw.

Battery Capacity (mAh)

Average Current Draw (mA)

Battery Voltage (V)

Duty Cycle (%)

Self-Discharge (%/month)

Discharge Efficiency (%)

Tab to move between fields

Runtime (hours)

16.49

Runtime (days)

0.69

Runtime (minutes)989.4

Effective Current (mA)100

Usable Capacity (mAh)1,649

Total Energy (Wh)7.4

Usable Energy (Wh)6.1

Power Draw (mW)370

Power Consumption W0.37

Days To Depletion0.69

How to Use This Calculator

Enter your battery capacity (mAh), average current draw (mA), and nominal voltage (V).
Set the duty cycle (%) — the fraction of time the circuit is actively drawing full current.
Enter self-discharge rate (%/month) and discharge efficiency (%) for your battery chemistry.
Review runtime in hours and days, effective current draw, and usable capacity.

How the result changes with Average Current Draw (mA)

Battery Capacity (mAh): Battery rated capacity in milliamp-hours (e.g. 18650: 2600, AA: 2500, CR2032: 225).
Average Current Draw (mA): Average current your circuit draws in milliamps.
Battery Voltage (V): Nominal battery voltage (e.g. LiPo: 3.7V, AA: 1.5V, 9V: 9V).
Duty Cycle (%): Percentage of time the circuit is actively drawing current (100% = always on).
Self-Discharge (%/month): Monthly self-discharge rate (NiMH ~20%, Li-ion ~2-3%, alkaline ~0.3%).
Discharge Efficiency (%): Usable fraction of rated capacity (typically 80-90% for lithium, 70-85% for alkaline).

Runtime (hours): Estimated battery life in hours.
Runtime (days): Estimated battery life in days.
Runtime (minutes): Estimated battery life in minutes.
Effective Current (mA): Average current accounting for duty cycle.
Usable Capacity (mAh): Effective capacity after efficiency and self-discharge losses.
Total Energy (Wh): Total energy stored in the battery.
Usable Energy (Wh): Usable energy after losses.
Power Draw (mW): Average power consumption of the circuit.

Identify Input Parameters
4 parameters
Battery Capacity (mAh) = 2000, Average Current Draw (mA) = 100, Battery Voltage (V) = 3.7, Duty Cycle (%) = 100 = 6 input(s) provided
Calculate Runtime
16.49 = 16.49
Calculate Runtime
Runtime = runtimeHours / 24
0.69 = 0.69
Calculate Runtime
Runtime = runtimeHours * 60
989.4 = 989.4
Calculate Effective Current
Effective Current = avgCurrentMa * (dutyCyclePct / 100)
100 = 100