Continuous sensing of respiratory volume is valuable for evaluating exercise ability and managing health condition. However, continuous sensing of respiratory volume without interfering with exercise and breathing is difficult using conventional methods. This research proposed a novel sensing method of respiratory volume using electromagnetic induction coils placed on ventral and dorsal aspects of the chest. The induced signal changed due to chest movement from breathing, and was used for estimating respiratory volume. This paper revealed experimentally the effective frequency of the electromagnetic wave for achieving high sensitivity. By measuring and analysing the output signal of the proposed system and chest displacement using an optical motion tracker during rest and stepping exercise, we showed that the system can detect chest displacement caused by respiration with adequate accuracy. An experiment in which we measured the output of the proposed system and the respiratory volume using a calibrated owmeter showed that our system can estimate the respiratory volume within an error of 0.228L.