We describe a new method to estimate the geometry of a room given room impulse responses. The method utilises convolutional neural networks to estimate the room geometry and uses the mean square error as the loss function. In contrast to existing methods, we do not require the position or distance of sources or receivers in the room. The method can be used with only a single room impulse response between one source and one receiver for room geometry estimation. The proposed estimation method can achieve an average of six centimetre accuracy. In addition, the proposed method is shown to be computationally efficient compared to state-of-the-art methods.