A wound therapy system includes a negative pressure circuit, a pump, a pressure sensor, and a controller. The negative pressure circuit applies negative pressure to a wound. The pump is fluidly coupled to the negative pressure circuit and produces a negative pressure at the wound or within the negative pressure circuit. The pressure sensor measures the negative pressure within the negative pressure circuit or the wound. The controller performs a testing procedure including a first drawdown period, a leak rate determination period, a vent period, and a second drawdown period. The controller is configured to receive one or more pressure measurements of the pressure sensor over the leak rate determination period to determine a leak rate parameter, monitor an amount of elapsed time over the second drawdown period to determine a drawdown parameter, and estimate a volume of the wound based on the leak rate parameter and the drawdown parameter.