The consumption of fragrance oil depends on your diffuser model, intensity level, hours of operation per day and days per week. As a general principle for our residential diffuser models, at a medium intensity level, working seven days a week from 8:00AM to 20:00PM the consumption of oil is approximately 100ml per month for the Portable Mini Diffuser, 200ml for M10, 500ml for M30/L50 and 1000ml for L150. This is just an estimate and the actual consumption level can vary based on your diffuser and program settings.