Watermelon Water Requirement Calculator
Work out the seasonal and per-irrigation water requirement of watermelon (FAO-56 ETc = ET₀ × Kc, peak Kc 1) for your field, climate, soil and irrigation method.
Water generously through vine growth and fruit sizing, then cut back sharply in the last 7–10 days — excess water at ripening dilutes sweetness and cracks fruit. Drip suits the crop and keeps foliage dry.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.
Farmers and irrigation planners use the free Watermelon Water Requirement Calculator to turn the FAO-56 crop coefficients for watermelon into a real seasonal water volume and an irrigation interval for their own field — no agronomy tables, works offline.
About Watermelon Water Requirement Calculator
Watermelon needs 400–600 mm, but a controlled dry-down in the final ripening week is what concentrates sugars. This calculator uses the FAO-56 method — crop evapotranspiration ETc = ET₀ × Kc — with watermelon's own crop coefficients (Kc 0.4 initial, 1 mid-season, 0.75 late) across a 110-day season. Pick your climate band (which sets reference ET₀), irrigation method (drip, sprinkler, pivot or surface — each with its own efficiency) and soil texture, and it returns the seasonal water need in cubic metres, the peak daily demand, the net depth per irrigation and how many days to wait between irrigations.
How to use Watermelon Water Requirement Calculator
- 1Enter your field area and choose the climate band matching your season.
- 2Select your irrigation method and soil texture.
- 3Read the seasonal water volume, peak daily demand and irrigation interval, then follow the scheduling note.
Why use Watermelon Water Requirement Calculator?
- ✓Uses watermelon's real FAO-56 Kc curve, not a flat factor
- ✓Accounts for drip / sprinkler / pivot / surface efficiency
- ✓Gives seasonal volume, peak daily need and an irrigation interval
- ✓Free, instant and fully in-browser — works offline in the field
Frequently asked questions
How much water does watermelon need?+
Watermelon needs 400–600 mm, but a controlled dry-down in the final ripening week is what concentrates sugars. The exact figure depends on climate and season length; this tool sums ET₀ × Kc across the crop's 110-day growth stages for your conditions.
Should I stop watering watermelon before harvest?+
Reduce it sharply in the final 7–10 days. The fruit has reached size by then, and easing water concentrates sugars (Brix) and prevents cracking. Heavy late irrigation gives big, bland, split melons.
How much water does watermelon need?+
About 400–600 mm, peaking during vine growth and fruit sizing. The calculator scales this to your field and method; remember to apply the late-season dry-down it cannot schedule for you.
What is ET₀ and Kc?+
ET₀ (reference evapotranspiration) is how fast a standard grass surface loses water in your climate. Kc (crop coefficient) scales it to a specific crop and growth stage. Crop water use ETc = ET₀ × Kc — the basis of FAO-56 irrigation scheduling.
Is this calculator free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline in the field and your data never leaves the device.
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