Watering Schedule Calculator
Calculate how much water your garden needs per week based on plant type, climate, and recent rainfall.
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How to use this calculator
Each mm of water over 1 m² equals 1 litre. Subtract recent rainfall from the weekly requirement and multiply by garden area. Session duration depends on flow rate.
- 1
Enter your garden area in square metres.
- 2
Select the dominant plant type in your garden.
- 3
Choose your climate zone.
- 4
Enter any rainfall received this week to deduct from the requirement.
- 5
Read the water volume, sessions needed, and hose or sprinkler run time.
Frequently asked questions
How do I know how much rainfall my garden received?
A simple rain gauge placed in the garden gives an accurate reading. Many weather apps also provide suburb-level rainfall totals. Subtract this amount from the weekly requirement to avoid overwatering.
Is it better to water in the morning or evening?
Morning watering is best. It allows foliage to dry during the day, reducing fungal disease risk. Water applied to roots in the morning is available to plants during the hottest part of the day. Evening watering leaves moisture on leaves overnight.
How do I convert millimetres of water to litres?
1 mm of water over 1 m² equals exactly 1 litre. If your garden is 20 m² and needs 25 mm, you need 500 litres.
Watering Schedule Calculator — Garden Water Needs by Plant & Climate
Why Plant Type and Climate Both Matter
Vegetables and lawns need frequent watering (25–30 mm/week in temperate climates) while established trees and succulents need far less. Arid climates increase evapotranspiration by up to 50%, so the same plant needs significantly more water than in a humid climate.
Deep vs Frequent Watering
Deep, infrequent watering (2–3 times per week) encourages roots to grow deeper into the soil, making plants more drought-tolerant. Light daily watering keeps moisture near the surface, creating shallow roots that are vulnerable to heat stress.
Smart Irrigation Tips
Drip irrigation delivers water directly to roots with minimal evaporation loss — far more efficient than overhead sprinklers in arid climates. Mulching around plants reduces soil moisture evaporation by up to 70%, cutting watering needs significantly.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →