Tomato Water Requirement Calculator
Work out the seasonal and per-irrigation water requirement of tomato (FAO-56 ETc = ET₀ × Kc, peak Kc 1.15) for your field, climate, soil and irrigation method.
Even moisture during fruit set and development prevents blossom-end rot and fruit cracking; drip with mulch is ideal. Avoid wetting foliage to reduce blight. Ease water slightly at ripening for better flavour.
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 Tomato Water Requirement Calculator to turn the FAO-56 crop coefficients for tomato into a real seasonal water volume and an irrigation interval for their own field — no agronomy tables, works offline.
About Tomato Water Requirement Calculator
Tomato needs 400–600 mm and rewards drip irrigation that keeps the root zone evenly moist through the long fruiting flush. This calculator uses the FAO-56 method — crop evapotranspiration ETc = ET₀ × Kc — with tomato's own crop coefficients (Kc 0.6 initial, 1.15 mid-season, 0.8 late) across a 145-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 Tomato 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 Tomato Water Requirement Calculator?
- ✓Uses tomato'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 tomato need?+
Tomato needs 400–600 mm and rewards drip irrigation that keeps the root zone evenly moist through the long fruiting flush. The exact figure depends on climate and season length; this tool sums ET₀ × Kc across the crop's 145-day growth stages for your conditions.
Does irregular watering cause blossom-end rot in tomato?+
Yes — blossom-end rot is a calcium-delivery failure driven mainly by uneven soil moisture. Steady drip irrigation plus adequate calcium prevents it far more reliably than spraying calcium onto fluctuating-moisture plants.
How much water do tomatoes need?+
About 400–600 mm over the season, peaking at fruit development (Kc ~1.15). The calculator scales this to your area, climate and method and suggests an irrigation interval from your soil's water-holding capacity.
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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