Irrigation Run-Time Calculator Australia: How Long Should I Water?
Tell us what you are watering, your soil and your system. Get a run time per watering, a weekly schedule and the litres used.
Step 1: What are you watering?
Pick the main plant type in this watering zone.
Your soil
Is the soil mulched?
Step 2: Your watering system
Choose how you want to describe your system. The flow test is the most accurate for any system.
Starting values only. Check your dripline packaging for the real flow and spacing.
Bucket test: run your system into a bucket for 1 minute through its normal outlets, or time how long a 10 L bucket takes to fill from the tap, then work out litres per minute.
Catch-can test: place several straight-sided cans in the area, run the system for 15 minutes, measure the depth in mm and multiply by 4.
Step 3: Area and conditions
Your watering plan
Suggested schedule and tips
Want to cut your water use? Try the Garden Water Savings Calculator or work out your mulch needs with the Mulch Calculator.
How long should I water my garden?
The right run time depends on how much water your plants need each week and how quickly your system delivers it. A dripline that applies 20 mm an hour needs 45 minutes to deliver 15 mm, while a sprinkler that applies 10 mm an hour needs 90 minutes. This calculator turns your system’s flow, your area and your soil into minutes per watering and a weekly schedule. One litre spread over one square metre is 1 mm of water, which is how the numbers connect.
Typical summer water needs used here
| Garden type | Weekly need in summer | Notes |
|---|---|---|
| Vegetable garden | About 30 mm | Shallow roots, so water often |
| Lawn | About 25 mm | Deep, less frequent watering builds roots |
| Flower beds and shrubs | About 20 mm | Mulch helps most here |
| Fruit trees | About 25 mm | Water at the drip line, not the trunk |
| Native garden | About 10 mm | Established natives need much less |
How this calculator works
Weekly need is a rule-of-thumb figure for the plant type, reduced in cooler seasons (spring 70%, autumn 60%, winter 30% of summer), increased by 30% in a hot spell and reduced by 20% if the soil is mulched. The number of waterings comes from a rule-of-thumb limit on how much water each soil holds per watering (sandy 10 mm, loam 15 mm, clay 20 mm). Run time is the depth per watering divided by your application rate. These are general guides, not weather forecasts, and they are not based on Bureau of Meteorology data. Plant size, shade, wind and rain all change real needs, so check the soil a few centimetres down and adjust. Follow any local water restrictions that apply to you.
Frequently asked questions
How long should I run my dripline?
Divide the water your plants need per watering by your system’s application rate in mm per hour. This calculator does that for you from your emitter flow and spacing, or from a simple bucket test.
How do I measure my sprinkler’s flow rate?
Use a bucket test to find litres per minute, then enter it with your watered area. Or use cans placed around the area for 15 minutes and multiply the depth in millimetres by 4 to get mm per hour.
Is it better to water deeply or often?
Deeper, less frequent watering encourages deeper roots in lawns and established plants. Sandy soils hold less water, so they need smaller, more frequent waterings.
When is the best time of day to water?
Early morning is usually best because there is less evaporation and wind, and leaves dry during the day. Check any local watering time restrictions.
What is cycle and soak?
If your system applies water faster than the soil can absorb it, split the run into shorter cycles with a break in between. This reduces runoff, especially on clay and slopes.
Garden Yard Australia: free garden tools for Australian gardeners. Results are estimates, so check your soil moisture and local conditions.