Watering Schedule Calculator

How does the watering schedule calculator work?

Weekly need in millimetres = a base figure for the plant type × a climate multiplier. Rainfall you enter is subtracted, and the remainder is multiplied by the garden area. One millimetre over one square metre is one litre, so the result is in litres per week.

What base figures does it use per plant type?

Lawn 25 mm per week, vegetables 30, flowers 20, shrubs 15, trees 10 and succulents 5. These are the figures built into this tool; real needs depend on species, soil, season and local conditions, so treat them as a starting point.

What are the climate multipliers?

Arid 1.5, semi-arid 1.25, temperate 1.0, humid 0.8 and tropical 0.7. They scale the base figure up or down and are applied to every plant type in the same way.

How are the number of sessions chosen?

From the net weekly need after rain: under 5 mm gives 0 sessions, up to 15 mm gives 1, up to 25 mm gives 2, and above 25 mm gives 3. The water is divided evenly between sessions.

Where do the hose and sprinkler minutes come from?

The tool divides the weekly litres by the number of sessions and by a fixed flow rate: 10 litres per minute for a hose and 25 for a sprinkler. Measure your own output with a bucket and timer, since pressure and fittings change it.

Why can it show litres but zero sessions?

When the net need is above zero but under 5 mm, the tool still lists the litres required but schedules no session. For a 15 m² tree bed in the tropical setting with 3 mm of rain, it reports 60 L and 0 sessions. Read that as a small top-up rather than a scheduled watering.

What happens when rain covers the whole need?

If rainfall equals or exceeds the weekly requirement, the tool reports 0 L and no sessions, because the net need cannot go below zero.

Does it account for soil type, slope or evaporation?

No. It also has no daily weather, wind or temperature input. It uses one rainfall total for the week and a single multiplier per climate zone.