LiPo Battery Calculator
Estimate voltage, watt-hours, max current, flight time, and charging time for your LiPo pack.
Why use a LiPo battery calculator?
LiPo batteries are the heart of many RC systems: drones, RC planes, cars, boats, and robotics projects. A quick calculator helps you understand whether a battery pack is appropriate for your setup before you plug it in and fly.
With the right numbers, you can avoid common issues like voltage sag, underpowered performance, overheating packs, and overly aggressive charge rates. This page gives you practical calculations in seconds.
What this calculator estimates
- Nominal pack voltage and full-charge voltage
- Total energy in watt-hours (Wh)
- Maximum continuous discharge current (A) from C rating
- Estimated runtime based on average current draw and reserve
- Recommended 1C charge current and estimated charge time
Core LiPo formulas
1) Voltage by cell count
Each LiPo cell is about 3.7V nominal and 4.2V when fully charged:
- Nominal pack voltage = Cells × 3.7V
- Full charge voltage = Cells × 4.2V
- Storage voltage (approx) = Cells × 3.8V
2) Maximum continuous current
Convert mAh to Ah, then multiply by C rating:
- Capacity (Ah) = mAh ÷ 1000
- Max continuous current (A) = Capacity (Ah) × C rating
3) Energy in watt-hours
A better way to compare battery packs:
- Energy (Wh) = Capacity (Ah) × Nominal Voltage (V)
4) Runtime estimate
Using average current draw and a safety reserve:
- Usable capacity (Ah) = Capacity × (1 - reserve%)
- Runtime (hours) = Usable Ah ÷ Average current (A)
How to interpret your results
If your average current draw is close to or above the battery’s continuous current rating, your pack may run hot and sag heavily under load. In that case, a larger pack or higher C rating is usually a better choice.
Likewise, if your charge current corresponds to a very high C-rate, charging may reduce cycle life. Unless your battery specifically supports fast charging, staying near 1C is a conservative and healthy baseline.
Example: 4S 1500mAh 75C
- Capacity: 1500mAh = 1.5Ah
- Nominal voltage: 4 × 3.7 = 14.8V
- Full voltage: 4 × 4.2 = 16.8V
- Max continuous current: 1.5 × 75 = 112.5A
- Energy: 1.5 × 14.8 = 22.2Wh
If your aircraft averages 30A and you keep a 20% reserve, expected runtime is roughly a few minutes, which is typical for high-performance freestyle or racing setups.
LiPo safety and best practices
- Do not over-discharge; land before any cell gets too low under load.
- Store packs near 3.8V per cell for longevity.
- Charge on a non-flammable surface and monitor charging sessions.
- Use balanced charging and inspect packs for puffing or damage.
- Match connector, wire gauge, and ESC capability to expected current.
FAQ
Is a higher C rating always better?
Not always. Higher C packs can reduce voltage sag and run cooler at high loads, but they may cost more and sometimes weigh more. Pick what your application actually needs.
Can I estimate flight time exactly with this calculator?
No calculator can perfectly predict runtime because throttle behavior, weather, prop choice, motor efficiency, and payload all change real-world consumption. Treat runtime as a planning estimate.
Why use Wh instead of just mAh?
Wh includes voltage, so it reflects total energy better than mAh alone. This makes comparisons across 3S, 4S, 6S, and other pack types much more meaningful.
Final note
This LiPo battery calculator is a practical starting point for selecting packs, planning flight sessions, and charging responsibly. Combine these calculations with logs from your charger or telemetry data for the most accurate tuning.