# Crop Water Budget Calculator

Convert entered ETo, crop factor, effective rain and irrigation efficiency to litres.

[Open this tool](https://whatson.pk/gardening-water-need-calculator/)

Category: Gardening

Crop water demand starts with entered weather and crop factors, then rain offsets part of the requirement.

Supply ETo, crop factor and effective rainfall on matching units. Apply efficiency to compare irrigation litres.

## Inputs and controls

* Reference ET per day (mm/day). Allowed range: 0 to 100
* Entered crop coefficient (Kc). Allowed range: 0.01 to 3
* Days in period (days). Allowed range: 1 to 365
* Effective rain across period (mm). Allowed range: 0 to 10000
* Garden area (m²). Allowed range: 0.01 to 1000000
* Application efficiency (%). Allowed range: 0.01 to 100

## How to use

* Enter reference ET per day, entered crop coefficient, days in period and effective rain across period.

* Enter garden area and application efficiency.

* Select Calculate result. Read the returned values alongside the assumptions below before copying, exporting or acting on the result.


## Why use this tool

The staged calculation separates crop demand from the larger water amount needed after application losses.


## Before relying on the result

ETc equals ETo × Kc. ETo and Kc are entered values, not weather forecasts; effective rain is already net of losses.


## Tool limitations

ETc equals ETo × Kc. ETo and Kc are entered values, not weather forecasts; effective rain is already net of losses.

## Questions

### Is rainfall fetched automatically?

No. Enter suitable values for the period and site. Effective rain should already account for its relevant losses.

### What should I check before using Crop Water Budget Calculator?

Check Reference ET per day, Entered crop coefficient, Days in period and Effective rain across period. Use the exact units shown beside the controls and replace any example values with your own inputs.

Source page last modified (UTC): 2026-10-04T13:08:12+00:00

This profile describes the tool. It does not execute it or supply a professional certification.