Acetone constitutes 58% of the volatile organic compounds found in human breath. Acetone in breath is proven to be a biomarker for type I diabetes. Portable and sensitive metal oxide semiconductor-based gas sensor with Tungsten Oxide (WO3) thin film as the sensing layer has been used to measure the concentration of Acetone in breath. Acetone gas being a reducing gas decreases the resistance of thin film when it comes in contact of the sensor. The gas sensor is fabricated, characterized and tested for various concentrations of Acetone gas. A linear calibration curve is obtained on the log scale for predicting any concentration in the novel range of 10 ppm to 300 ppm at 300 °C in the sensor fabricated using RF Magnetron sputtering method. The gas sensor is portable and easy to handle with the chip size of 5mm × 5mm and thin film thickness of 100 nm. The efficiency is optimized by operating it at temperature 300 °C with minimum response time and recovery time © 2018 IEEE.