The rate curve describes how the stick position on your radio is converted to commands to the flight controller to tell it how fast to rotate. In contrast to "angle" or "horizon" mode, where the stick tells the quad how far to tilt, stick position in "acro" mode commands the quad how fast to rotate. The rate curve is for this mode, and choosing the right rate profile lets you choose how the quad responds to your stick inputs.
The rate calculator lets you choose from several rate types, all of which are from the Betaflight firmware. Each curve has a slightly different set of parameters to control its shape. While the different curves aren't identical, they're similar enough, and you can use the fit button to perform a one-time conversion from one set of curve parameters to another. To watch changes between curves in realtime, use link to bind two curves to each other: when one changes, the other will be updated to its best approximate match.
In any of the curves, Expo sets how exponential the curve is, or rather how flat the curve is towards the center versus towards the end output ranges. A smaller expo means a more linear feel across the stick range, and a larger expo and/or higher max rate means the stick is more sensitive the further from the center you get. The center tangent toggle shows the center sensitivity, which is the slope at the center of the curve. You can move your mouse over the range to see the gain (slope of the line) at any point, which describes the sensitivity of the curve relative to straight line between 0 and the maximum rate. The elbow toggle shows where the curve crosses over, which is the point where the curve becomes more sensitive than a straight line would be.
The throttle curve turns throttle stick position into the throttle percentage the motors are asked for.
The throttle curve can be calculated in two different ways. Prior to the 2025.12 Betaflight release, it was defined as a midpoint and expo alone. The 2025.12 release added a hover point, which is the throttle percentage that keeps the quad in a hover. The combination of hover point and midpoint are used to determine where the curve is built around, and expo flattens the curve through it. Use mid & hover to show the hover point and midpoint on the graph.
The legacy version of the throttle curve is no longer available in Betaflight firmware, but is still often the only configuration available in FPV simulators. You can use this calculator to convert between them as best as possible. Similar to the rate profiles, use fit and link for one-time and realtime conversion between curves.
The throttle parameters describe a smooth curve, but the flight controller never evaluates it in flight. At startup it samples that curve in twelve places and stores those numbers as a lookup table. From then on, every throttle input is calculated by finding the two nearest entries and drawing a straight line between them. Turn on sample points to see where the twelve samples are calculated: the visible kinks between them are real, not a drawing artifact. Twelve points is close enough that the error is small, but it is not zero. Note that the legacy curve internally stores its twelfth sample at 110%, so it will not be visible on the graph.
Betaflight does not use the entire stick range by default. Anything at
or below min_check counts as "off", which is important
for purposes such as "do not arm unless the throttle is off". This is
a number defined in a range of 1000-2000 microseconds, which is a
detail of how the radio control protocol works. The default value is
1050, meaning the bottom 5% of the throttle stick range is
disregarded. The effect of excluding this 5% range is that the entire
throttle curve is calculated from the remaining 95% range, meaning
everything is shifted slightly to the right. If you're looking for
this in Betaflight Configurator, it's in the Receiver tab.
The throttle percentages your OSD and your blackbox log report have
already had the min_check scaling applied to them, so a
hover throttle read from the OSD can be used as your hover value as-is
with no correction needed.
In 3D mode throttle is taken from the full range in both
directions, and min_check is not applied.
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