Irrigation Water Calculator

Farmers and irrigators use water meters to track how much water they apply to a field — but converting raw meter readings into usable depth and rate figures takes several steps. Enter your beginning and ending meter readings, select your water flow meter type, and provide your acres irrigated and irrigation duration into the Irrigation Water Calculator to see water applied in inches. Secondary outputs include total water used (gallons), application rate (inches/hour), and water per acre (gallons/acre).

Enter the meter reading when irrigation starts

Enter the meter reading when irrigation ends

acres

Total area being irrigated

hours

Total hours of irrigation

Results

Water Applied

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Total Water Used

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Application Rate

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Water per Acre

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Frequently Asked Questions

What units are typically used on irrigation flow meters?

Common irrigation flow meter units include Gallons x 100, Gallons x 1000, Acre-Feet x 0.001, and Acre-Inches x 0.01. The units are usually displayed just below the rolling numbers on your meter, similar to an odometer.

How do I read my irrigation meter correctly?

Note the meter reading at the beginning of irrigation (when you turn on the system) and at the end (when irrigation stops). Enter only the numbers visible on the totalizer display, without decimals.

What if my meter totalizer has rolled over during irrigation?

If your meter has rolled over (reset to zero), you may need to add the maximum reading value to your ending reading or enter a 1 in front of the ending reading to make calculations work correctly.

How many inches of water do crops typically need?

Most crops need 1-2 inches of water per week, including rainfall. Cool-season grasses need about 1 inch per week, while warm-season crops may need 1.5-2 inches during peak growing season.

What is a good irrigation application rate?

Application rates should match your soil's infiltration rate to avoid runoff. Sandy soils can handle 0.5-1.0 inches per hour, while clay soils typically handle 0.1-0.3 inches per hour.

How do I convert between different water measurement units?

One acre-inch equals 27,154 gallons. One acre-foot equals 325,851 gallons or 12 acre-inches. These conversions help compare water usage across different measurement systems.

Why is measuring irrigation water important?

Accurate water measurement helps optimize crop yields, reduce water waste, manage irrigation costs, and comply with water use regulations. It also helps identify system inefficiencies.

How often should I check my irrigation water usage?

Check water usage weekly during growing season to ensure you're applying the right amount. Daily monitoring is recommended during hot, dry periods or when establishing new crops.