The calculator allows for the user to enter readings from Watermark brand sensors. The user enters the readings for the rooting depth, the effective rooting depth for the stage of growth, the soil type and the Managed Allowable Depletion (MAD). The app calculates the average centibar reading for the provided values, the available water remaining and provides the stress level. Days to required irrigation can then be easily determined. How much water is required for last irrigation is also calculated and adjusted for irrigation efficiency.