The maximum boost capacity a Rocket League car can hold is 100. Boost is the orange resource used to accelerate rapidly, fly through the air, recover after jumps, and reach supersonic speed.
A player can refill the tank by collecting boost pads around the arena. Small pads add 12 boost, while the large corner and midfield pads refill the tank completely to 100. Boost is not stored beyond that limit, so collecting a full boost pad while already full provides no extra reserve.
The number 100 can be confusing because a full tank does not mean unlimited boost. Continuous boosting drains the meter quickly, and aerial plays can consume much of it before the car returns to the ground. Efficient players therefore manage boost as carefully as positioning and momentum.
Boost management is also central to team strategy. Taking a large pad may leave a teammate without one, while rotating through small pads can preserve pressure without abandoning the play. The boost meter is therefore both a movement resource and a tactical resource.