Irrigation Water and Runtime Calculator
Estimate irrigation volume and runtime from area, entered target water depth, effective rain, application efficiency and measured flow.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Subtract entered effective rainfall from the target depth, stopping at zero. Multiply by area for net water volume, divide by application efficiency for gross delivered water, then divide by measured flow for runtime.
Net depth=max(0,target−effective rain); gross volume=area×net depth/efficiency; time=gross volume/flow
Worked example
100 m² needing 10 mm, with 2 mm effective rain and 80% efficiency, needs 1000 L gross irrigation. At 20 L/min the runtime is 50 minutes.
Assumptions and input details
Water-depth and efficiency values are supplied by the user; no crop requirement, soil condition, rainfall forecast or safe watering schedule is inferred. Effective rainfall is the amount already usable for the target, not necessarily measured total rain. Uniform area application and constant measured flow are assumed. Runoff, infiltration limits and distribution differences require separate assessment. One square metre times one millimetre equals one litre.
References: UF IFAS irrigation water measurement
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
The 36 volume definitions distinguish US liquid, US dry and Imperial measures. Cups carry an explicit definition. Japanese shō is 2401/1331 L and a gō is one tenth of it; the explicitly labelled 180 mL rice cup is separate.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · UK Imperial definitions · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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