Calculate Battery Capacity and Energy
Start with 350 mAh, or enter another rating. Add pack details for useful amp-hour and watt-hour estimates.
Formula Used
The basic conversion changes milliamp hours into amp hours.
For a battery pack, parallel strings add capacity. Series cells add voltage.
These formulas provide estimates. Actual output depends on cell condition, temperature, load, and protection settings.
How to Use This Calculator
- Enter 350 mAh, or replace it with your battery rating.
- Enter one parallel string for a single battery.
- Add parallel strings when identical cells share the load.
- Add series cells to estimate total pack voltage.
- Enter nominal cell voltage, such as 3.7 V.
- Choose a usable percentage for your operating limit.
- Select decimal places and press the conversion button.
- Review amp hours, voltage, and watt-hour estimates above.
Example Capacity Conversions
| Battery rating | Calculation | Amp hours | Energy at 3.7 V |
|---|---|---|---|
| 350 mAh | 350 ÷ 1,000 | 0.35 Ah | 1.295 Wh |
| 500 mAh | 500 ÷ 1,000 | 0.50 Ah | 1.850 Wh |
| 1,000 mAh | 1,000 ÷ 1,000 | 1.00 Ah | 3.700 Wh |
| 2,500 mAh | 2,500 ÷ 1,000 | 2.50 Ah | 9.250 Wh |
Understanding 350 mAh in Amp Hours
A 350 mAh battery stores 0.35 amp hours of rated capacity. The conversion is simple. Divide milliamp hours by 1,000. This value helps you compare batteries that use different capacity labels. It also makes battery specifications easier to read.
Capacity alone does not describe every battery. Voltage matters when you estimate energy. A 0.35 Ah cell at 3.7 volts stores about 1.295 watt hours. A similar capacity at a different voltage stores a different energy amount. Use watt hours when comparing different battery chemistries or voltages.
Why Parallel and Series Connections Matter
Parallel battery strings increase available amp hours. Two identical 350 mAh cells in parallel provide 0.70 Ah before losses. Their voltage stays near the same. Series connections work differently. They increase voltage, while rated amp hours stay unchanged. A two-series, two-parallel pack has higher voltage and greater capacity.
Real packs rarely deliver their full label rating. Temperature, age, current draw, and battery protection reduce usable capacity. The usable-capacity setting lets you apply a realistic percentage. For example, an 85 percent setting estimates energy available before normal operating limits are reached.
Choosing a Useful Precision Level
Use two or three decimal places for everyday battery work. This is usually enough for a 350 mAh conversion. More decimal places can help with engineering notes or spreadsheet exports. They do not make measurements more accurate. The final result is only as reliable as the battery data supplied.
Check whether a manufacturer lists typical or minimum capacity. Typical capacity is common for comparisons. Minimum capacity can be better for guaranteed designs. Never combine mismatched cells in a pack. Different capacities, ages, or chemistries can cause uneven charging and discharging.
Applying Results to Devices
For a low-power sensor, divide usable amp hours by average current in amps. A device drawing 0.07 amps from a 0.35 Ah battery could run for about five hours under ideal conditions. Actual runtime may be shorter. Startup surges, voltage cutoff, and conversion losses all matter.
For rechargeable packs, use the calculator as an estimate rather than a charging plan. Follow the cell maker's approved charge voltage and current. Use suitable protection and balancing hardware for multi-cell packs. Battery safety requires correct wiring, compatible cells, and an appropriate enclosure.
Making Better Comparisons
Convert every candidate battery to amp hours first. Then calculate usable watt hours at its nominal voltage. Compare size, weight, discharge rating, cycle life, and safety requirements. A larger value is not always the better option. The best battery supports your device load and operating conditions.
This calculator starts with 350 mAh because it is a common small-cell rating. Replace that value whenever needed. The conversion rule remains the same. Enter complete pack details for useful voltage and energy estimates. Record actual test results to refine future estimates. Keep manufacturer specifications as the final reference for critical designs.
Frequently Asked Questions
1. What is 350 mAh in amp hours?
350 mAh equals 0.35 Ah. Divide 350 by 1,000 to convert milliamp hours into amp hours.
2. What formula converts mAh to Ah?
Use Ah = mAh ÷ 1,000. This works for every battery capacity value measured in milliamp hours.
3. Does a series connection increase amp hours?
No. Identical cells in series increase voltage. The rated amp-hour capacity remains the same as one cell string.
4. Does a parallel connection increase amp hours?
Yes. Parallel strings add capacity. Two matching 350 mAh cells in parallel provide about 0.70 Ah before operational losses.
5. How do I calculate watt hours?
Multiply amp hours by nominal voltage. A 0.35 Ah battery at 3.7 V stores approximately 1.295 Wh.
6. Why use a usable capacity percentage?
It estimates capacity available within your chosen operating limits. Devices often stop before a battery reaches its full rated discharge depth.
7. Can I enter a capacity other than 350 mAh?
Yes. Replace 350 with any positive mAh rating. The calculator uses the same conversion formula for each value.
8. Is mAh the same as watt hours?
No. mAh measures electrical charge. Watt hours measure energy and require both capacity and voltage for calculation.
9. How can I estimate runtime?
Divide usable amp hours by your device’s average current in amps. Real runtime changes with load spikes, temperature, and voltage cutoff.
10. Why can actual runtime be lower?
Battery age, cold conditions, high current, conversion losses, and protective cutoff settings can reduce available energy.
11. Is this calculator suitable for battery safety decisions?
Use it for estimates and comparisons. Follow manufacturer limits, approved charging procedures, proper protection, and qualified guidance for safety-critical battery systems.