How the Formula Works

This calculator estimates how long a multirotor drone can stay airborne on a single battery charge using two key electrical principles:

  1. Total Battery Energy (Watt-hours, Wh)
   Battery Energy (Wh) = (Battery Capacity (mAh) / 1000) × Battery Voltage (V)

The battery capacity in milliampere-hours is first converted to ampere-hours (Ah) by dividing by 1000, then multiplied by the nominal voltage to get the total energy stored in watt-hours.

  1. Total Current Draw (Amps)
   Total Current Draw (A) = Avg. Current per Motor (A) × Number of Motors

The average current drawn by each motor is multiplied by the total number of motors to get the total current the whole drone pulls from the battery.

  1. Estimated Flight Time (Hours)
   Flight Time (hours) = Battery Energy (Wh) / Total Current Draw (A)

The battery energy is divided by the total current draw. Since both are in compatible units (watts-hour / amps = hours), this directly gives the flight duration in hours. This is then converted to minutes by multiplying by 60.

Example

  • Battery: 2200 mAh, 14.8V (4S LiPo)
  • Motors: 4, each drawing 10A
Energy = (2200 / 1000) × 14.8 = 32.56 Wh
Draw   = 10 × 4 = 40 A
Time   = 32.56 / 40 = 0.814 hours ≈ 48.84 minutes

Assumptions & Limitations

  • Motor current draw varies with throttle, payload, and flight style — this uses an average.
  • Battery voltage sags under load as the pack discharges.
  • Wind, temperature, and payload affect real-world flight time.
  • Always test with a battery monitor or telemetry for real measurements.

FAQs

1. Why is my actual flight time lower than what the calculator shows?
Actual flight time is almost always lower because motors draw more current than the average when climbing, launching, or flying aggressively. Wind resistance and payload also increase current draw. It’s recommended to add a 20–30% safety buffer to the calculated result.

2. What is “C” rating and how does it relate here?
The C rating tells you how fast a battery can safely deliver current. If your total current draw (motors × amps) exceeds the battery’s max discharge rating (Capacity in Ah × C-rating), the battery may heat up or sag significantly, reducing flight time and possibly damaging the battery.

3. Should I use nominal or fully-charged battery voltage?
Use the nominal voltage (e.g., 14.8V for a 4S LiPo) as most motor and battery specs are based on this. Fully charged voltage (16.8V for 4S) would give an optimistic estimate.

4. Does the number of propeller blades affect the calculation?
Not directly in this calculator — propeller blade count affects the current draw per motor, which you input as “Avg. Current per Motor.” You should use a realistic average current for your specific prop-motor combination.

5. Can I use this for fixed-wing drones?
Yes, the same formula applies, but for fixed-wing aircraft the current draw varies much more with throttle and airspeed. The result becomes a useful ballpark, not a precise number.

6. What’s a good battery configuration for longer flights?
Generally, higher voltage batteries (6S vs 4S) with the same motor setup tend to be more efficient because lower current is drawn for the same power. However, heavier batteries also mean more weight to carry, so there’s an optimal balance for your specific frame and motor combo.

7. How accurate is this calculator?
It’s accurate to within ±10–20% for typical mid-throttle cruising if you input realistic average current values. For hover or aggressive flight styles, the error can be larger.

Reference Links