Battery Life Calculator

Use Glofell’s Battery Life Calculator to estimate device runtime from nominal battery capacity and the load’s average current draw. Capacity is commonly entered in amp-hours (Ah) or milliamp-hours (mAh), and may also be stated in watt-hours (Wh), making this a practical guide for power planning.

Battery Life

Battery Life Formula

Battery Life = Battery Capacity in mAh / Load Current in mA

Estimated

* This is an estimated output, based on ideal conditions.

Introduction

Understanding Battery Life Calculation

Battery life refers to the duration a device can operate before its battery requires recharging. Calculating this effectively requires understanding the relationship between capacity, consumption, and efficiency factors.

Key Concepts & Conversion

Before using the calculator, it is helpful to understand the units involved:

Amp-hour (Ah): A unit of electric charge. It represents the amount of energy charge in a battery that will allow one ampere of current to flow for one hour.
Milliamp-hour (mAh): This is the unit most commonly used for small electronics. 1 Ah = 1000 mAh.

Battery Size	Chemistry	Estimated Capacity (mAh)	Notes
AAA	Alkaline	1200	Standard remote batteries
	NiMH	800 – 1000	Rechargeable
AA	Alkaline	2700	Standard household use
	Lithium (Rechargeable)	3000	High drain devices
	NiMH	1700 – 2900
C	Alkaline	8000	Medium drain
	NiMH	4500 – 6000
D	Alkaline	12000	High capacity flashlights
	NiMH	2200 – 12000	Wide variance in quality
	Lithium-Primary (3.6V)	19000	Industrial use
9V (PP3)	Alkaline	565	Smoke detectors
	Lithium-Primary	1200	Long-life applications
	NiMH	175 – 300
6V Lantern	Alkaline	26000	Heavy duty lighting
CR2032	Lithium-Primary (3V)	240	Coin cell (BIOS, watches)
CR2016	Lithium-Primary (3V)	90	Thinner coin cell
1/10 D	Lithium-Primary (3.6V)	1000	Specialized industrial
4 Farad Cap	Capacitor	~1 mAh	Equivalent @ 1mA drain/1V drop

FAQ

How do you calculate how long a battery will last?

Divide the battery's total capacity by the circuit's power consumption. For instance, if your battery has a reserve capacity of 120 minutes, multiply that by 60 to get 7,200 – the number of seconds it can theoretically support the load.

How long does a 5000mAh battery last?

A 5,000 mAh battery can supply 100 mA for around 50 hours, 10 mA for 500 hours, or 1 mA for 5,000 hours. The actual time depends on the load.

Is a 4000mAh battery good?

A 4,000 mAh smartphone battery will generally last more than a day with moderate use. Since a larger battery takes longer to refill, fast charging is a useful feature to avoid long wait times.

Is it better to have a higher mAh?

mAh measures the energy capacity of a battery. Higher mAh generally means a longer runtime, because the battery can store more energy for the same voltage.

Is 50000mAh power bank allowed in flight?

A 50,000 mAh power bank must be carried in your hand luggage – it cannot be placed in checked baggage.

How can I improve my battery life?

To extend battery life, you can reduce screen brightness, set the screen to turn off sooner, disable keyboard sounds, restrict background apps, and enable battery saver mode.

At what percentage should I charge my phone?

The best practice is to charge your phone when it reaches 30–40% and unplug it at 80–90%. Keeping the charge level between 30% and 80% can help prolong the battery's lifespan.

How much can a 20000mAh charge?

A 20,000 mAh power bank with an actual capacity of about 13,300 mAh can charge a tablet or laptop roughly 1.5 times.

Is it OK to use phone while charging?

Using a phone while charging is safe, though the charging speed will be slower because power is used to keep the screen on and run background apps. To speed up charging, use airplane mode or turn the phone off.

How many hours does 10000mah last?

A fully charged 10,000 mAh power bank can last about 71 hours in ideal conditions. In real-world use, conversion losses mean the effective capacity is roughly 60%, so actual runtime may be shorter.