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Irrigation Calculator — Water & Scheduling

Units

Irrigation Details

Irrigation Schedule

Weekly Water
934.5 gal
1.50 inches
Per Session
467.3 gal
234 minutes
Frequency
2x
per week
Annual Cost
$243
48,594 gal/year
Equipment Needed
5 sprinkler heads

Water Usage Breakdown

Per Session467 gal
Per Week935 gal
Annual Usage48.6k gal

Plant Water Needs Reference

Plant TypeWater NeedsFrequency
Lawn1-1.5 inches/week2-3 times/week
Vegetables1-2 inches/week3-4 times/week
Flowers1 inch/week2-3 times/week
Shrubs0.5-1 inch/week1-2 times/week
Fruit Trees1-2 inches (deep)Once per week
ContainersDaily watering6-7 times/week

Watering Tips

Water Early Morning

Water between 4-10 AM when temperatures are cooler to minimize evaporation and allow foliage to dry before nightfall, reducing disease risk.

Deep and Infrequent

Water deeply but less frequently to encourage deep root growth. Light, frequent watering promotes shallow roots that are more vulnerable to drought.

Use Mulch

Apply 2-4 inches of organic mulch around plants to retain moisture, regulate soil temperature, and reduce water needs by up to 50%.

Check Soil Moisture

Insert your finger 2-3 inches into soil. Water when it feels dry at that depth. Consider using a moisture meter for accuracy.

Adjust for Weather

Reduce watering after rainfall. Install a rain sensor on automatic systems to prevent overwatering and save up to 30% on water costs.

Zone Your Garden

Group plants with similar water needs together. This allows you to customize irrigation schedules and avoid overwatering some while underwatering others.

Example Calculations

1Standard Lawn Irrigation

Inputs

Area2,500 sq ft
Plant typeLawn
SoilLoam
Sun exposureFull sun
IrrigationSprinkler
ClimateModerate

Result

Weekly Water2,336 gallons

Water depth: 1.5 inches (1.25 base x 1.0 loam x 1.2 full sun x 1.0 moderate). Weekly water: 2,336 gallons (1.5 x 2500 x 0.623). Water 2 times per week, 1,168 gallons per session. Needs 13 sprinkler heads with 200 sq ft coverage each. Annual cost: approximately $607 at $0.005/gallon.

2Vegetable Garden Watering

Inputs

Area400 sq ft
Plant typeVegetables
SoilSandy
Sun exposureFull sun
IrrigationDrip
ClimateHot/arid

Result

Weekly Water816 gallons

Water depth: 3.28 inches (1.5 base x 1.3 sandy x 1.2 full sun x 1.4 hot). Weekly water: 816 gallons (3.28 x 400 x 0.623). Water 4 times per week, 204 gallons per session. Install 45 drip emitters at 12-inch spacing (400/9 sq ft coverage). Annual cost: approximately $212. Mulch heavily to reduce evaporation.

3Drip System for Shrub Border

Inputs

Area800 sq ft
Plant typeShrubs
SoilClay
Sun exposurePartial shade
IrrigationDrip
ClimateModerate

Result

Weekly Water262 gallons

Water depth: 0.525 inches (0.75 base x 0.7 clay x 1.0 partial shade x 1.0 moderate). Weekly water: 262 gallons (0.525 x 800 x 0.623). Water 2 times per week, 131 gallons per session. Needs 50 drip emitters at 18-inch spacing (800/16 sq ft coverage). Annual cost: approximately $68. Deep watering encourages drought tolerance.

Frequently Asked Questions

Q

How much water does my lawn need per week?

Most lawns need 1 to 1.5 inches of water per week, including rainfall. This translates to about 0.62 gallons per square foot per inch, or 620-930 gallons per week for a 1,000 sq ft lawn. Water deeply 2-3 times per week rather than daily shallow watering to encourage deep root growth.

Q

What's the best time of day to water plants?

The best time to water is early morning between 4-10 AM when temperatures are cooler and wind is minimal. This reduces evaporation loss by up to 30% and allows foliage to dry before nightfall, minimizing disease risk. Avoid watering in the evening as prolonged moisture on leaves overnight promotes fungal diseases.

Q

How do I calculate drip irrigation emitters needed?

For drip irrigation, emitter spacing depends on plant type: vegetables need 12-inch spacing (1 per sq ft), shrubs need 18-inch spacing (1 per 2.25 sq ft), and trees need 24-inch spacing (1 per 4 sq ft). Use 0.5-2 GPH emitters based on soil type - lower flow rates for clay soil, higher for sandy soil.

Q

Does soil type affect watering frequency?

Yes, soil type significantly impacts watering needs. Sandy soil drains quickly and requires 30% more water with more frequent applications (3-4 times weekly). Clay soil holds moisture longer, needing 30% less water with less frequent watering (1-2 times weekly). Loam soil is ideal, requiring standard watering schedules.

Q

How much does irrigation cost annually?

Annual irrigation costs vary by region but average $0.003-$0.007 per gallon. A 1,000 sq ft lawn needing 800 gallons weekly costs approximately $125-290 per year. Drip irrigation can reduce costs by 30-50% compared to sprinklers due to better efficiency and reduced evaporation. Install rain sensors to save an additional 20-30%.

Q

Should I adjust watering in hot weather?

Yes, increase watering by 30-40% during hot, arid conditions above 90 degrees F. Plants lose more water through transpiration in heat. Also increase frequency for shallow-rooted plants and containers, which may need daily watering. Conversely, reduce watering by 20% in cool, humid weather below 70 degrees F.

See Also

  • Rain Barrel Calculator
  • Lawn Fertilizer Calculator
  • Mulch Calculator
  • Garden Soil Calculator

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Last Updated: Feb 13, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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