A C-rating is the maximum discharge current expressed as a multiple of capacity. 1C equals the pack's capacity in amps. A 1500 mAh (1.5 Ah) pack rated 75C can deliver up to 75 times 1.5, which is 112.5 amps continuously.

How is the maximum current calculated?

Max current in amps equals capacity in amp-hours times the C-rating. Capacity in mAh is divided by 1000 to get amp-hours first. So 1500 mAh at 75C is 1.5 times 75, equal to 112.5 A continuous.

What is the difference between continuous and burst?

Continuous is the current the pack can sustain indefinitely without overheating. Burst is a higher current it can deliver only for a few seconds, such as during a hard punch-out. Never design around burst as if it were continuous.

Are manufacturer C-ratings accurate?

Many hobby-grade packs overstate their C-rating for marketing. A real-world rule is to treat the printed continuous figure as optimistic and keep your actual draw well below it, perhaps 60 to 80 percent, for cooler cells and longer pack life.

How does this relate to flight time and ESC choice?

The continuous current limit must comfortably exceed your craft's average draw, and the burst limit must exceed peak draw. Your ESC rating must also clear the same peaks. Use a capacity calculator for flight time and an ESC sizing calculator for the controller.

LiPo C-Rating & Max Burst Current Calculator

A LiPo’s C-rating tells you how hard you can pull on it before you risk overheating, puffing, or fire. This calculator converts the C-ratings printed on your pack into real current limits in amps, separating the current you can draw all day from the brief burst the pack can survive.

How it works

The C-rating is a multiplier on capacity expressed in amp-hours:

capacity Ah     = capacity mAh / 1000
max continuous A = capacity Ah × continuous C
max burst A      = capacity Ah × burst C

Continuous is the figure to design around. Burst applies only for a few seconds, so leave headroom rather than running at the burst limit.

Example and tips

A 1300 mAh pack rated 100C continuous / 200C burst can deliver 1.3 × 100 = 130 A continuously and 1.3 × 200 = 260 A in a burst. Because hobby C-ratings are often optimistic, a safer working continuous limit is around 70% of that — roughly 90 A here. Keep your craft’s average draw below the continuous limit and its hardest punch below the burst limit, and your packs will stay cool and last far longer.