Drone Battery Capacity Calculator

Drone Battery Sizing

The battery is one of the most critical components in a drone build. Too small and flight time suffers; too large and the extra weight reduces efficiency.

Formula: Required mAh = (Total Current Draw × Flight Time in minutes) / 60 × 1000 / (1 - Reserve%)

Where:

• Total Current Draw (A) = Number of motors × Current per motor at hover
• Flight time = desired flight time in minutes
• Reserve = safety buffer (typically 20 to 30%; never fully discharge a LiPo)

Watt-hours (energy): Wh = mAh × Voltage / 1000

Current draw by drone type (per motor, at hover)

These are hover figures, and hover is much gentler than it feels. A 5-inch quad holding altitude sits at maybe 35% throttle, and 35% throttle is nowhere near 35% of peak current. Punch-outs on the same aircraft pull four to six times these numbers for a second or two.

If a figure you enter gives a battery far bigger than the packs people actually fly on that airframe, the current is the number to doubt. Working backwards from a known pack and a known flight time is the most reliable way to get it: a 1500 mAh 4S that lasts 4.5 minutes with 20% left in it is 1200 mAh over 4.5 minutes, which is 16A total, or 4A per motor on a quad.

Battery cell voltage:

• 1S = 3.7V nominal (3.0V min, 4.2V fully charged)
• 3S = 11.1V nominal
• 4S = 14.8V nominal
• 6S = 22.2V nominal

LiPo discharge rating (C rating): The C rating multiplied by the capacity in Ah gives the maximum continuous current. A 1500mAh 50C battery can supply: 1.5 × 50 = 75A continuous.

This is the part that catches people out, because C rating has to cover the peak, not the average. Size a pack on hover current and a 1500 mAh 4S needs about 11C, which is a figure no FPV pack is even sold at. Real 5-inch packs are 75C to 100C, and that is not marketing: a punch-out on that aircraft genuinely pulls 80 to 120A for a moment, and a pack that sags under it will brown out the flight controller mid-air. Treat the hover C rating as a floor and buy several times it.

Pack weight matters as much as capacity

A bigger battery buys flight time and then spends some of it carrying itself. Modern LiPo packs land around 130 to 150 Wh per kilogram once you count the casing, wiring and connector, so a 4S 1500 mAh pack (22.2 Wh) weighs roughly 160 g. On a 650 g quad that is a quarter of the all-up weight. Doubling to 3000 mAh adds 160 g and raises hover current with it, so flight time goes up by much less than double, and past a point it stops going up at all. That crossover is why 5-inch quads settled on 1300 to 1500 mAh rather than the biggest pack that fits.

Practical notes: LiPo batteries should never be discharged below 3.5V per cell (storage) or 3.0V per cell (absolute minimum). Always monitor cell voltage with a buzzer or battery alarm during flight. Flying aggressively increases current draw far above hover, so add extra buffer.