Garden Watering Needs
Calculate how much water a lawn or garden needs per week from the area, rainfall and irrigation efficiency, free online.
About this calculator
Most lawns and vegetable gardens need about 25 mm (1 inch) of water a week including rain. 1 mm of water on 1 m² is 1 litre. Required irrigation = (target − rainfall) × area ÷ efficiency. Sprinklers are 65–75% efficient; drip irrigation 90%.