Garden Irrigation Calculator - Weekly Volume, Cost and System Comparison

Every plant, every system, every number on one page

A 200 m2 mixed garden burns through 2000 liters of water every week during summer. Over a 16-week growing season that adds up to 32 m3 - and at $4.50/m3 the bill lands at $144 if you use sprinklers. Switch to drip irrigation and the same garden drinks 35% less because water goes straight to roots instead of evaporating off leaves and pavement. The calculator compares four irrigation methods, three plant categories and gives you the seasonal total in liters, cubic meters and dollars.

Irrigation system atlas

Manual (garden hose)

Efficiency: 70%

Cost: $20-40 (hose only)

Best for: small gardens under 50 m2

Cheapest option. Requires your time and attention. Uneven coverage - some spots get too much, others too little.

Sprinklers

Efficiency: 60-80%

Cost: ~$2.50/m2 installed

Best for: lawns 100-500 m2

Good for large flat lawns. Water drifts in wind and evaporates in heat. Not ideal for vegetable beds.

Drip irrigation

Efficiency: 90%

Cost: ~$3.50/m2 installed

Best for: vegetable beds, flower borders

Most water-efficient. Delivers water directly to roots. Reduces weed growth. Requires periodic flushing of emitters.

Automatic (sprinklers + controller)

Efficiency: 70%

Cost: ~$5/m2 + $150-400 controller

Best for: large lawns, vacation homes

Set-and-forget convenience. Rain sensor prevents overwatering. Same efficiency as manual sprinklers but zero effort.

How to use the irrigation calculator - step by step

Area to irrigate (m2) - measure only the parts you water: lawn, vegetable patches, flower beds. Exclude paths, patios and wild areas.
Plant type - lawns need 5 L/m2/week, vegetables 20 L, mixed areas 10 L. When in doubt, pick "Mixed."
Irrigation system - each system has a different efficiency. Drip wastes the least water (90% reaches roots), sprinklers the most (60-80%).
Water price (optional) - enter your local rate to see seasonal cost and savings from drip vs sprinklers.
Read the results - weekly demand, seasonal total, actual use after system losses, cost and installation estimate.

Water needs by plant type and area

Garden area	Lawn (5 L/m2)	Mixed (10 L/m2)	Vegetables (20 L/m2)
50 m2	250 L/week	500 L/week	1,000 L/week
100 m2	500 L/week	1,000 L/week	2,000 L/week
200 m2	1,000 L/week	2,000 L/week	4,000 L/week
500 m2	2,500 L/week	5,000 L/week	10,000 L/week

These are plant demand values. Actual water use depends on system efficiency (70-90%).

System comparison - cost, water use and payback

System	Efficiency	Install cost (200 m2)	Season cost ($4.50/m3)	Water used (season)
Manual (hose)	70%	$30	$206	45.7 m3
Sprinklers	70%	$500	$206	45.7 m3
Drip irrigation	90%	$700	$160	35.6 m3
Automatic	70%	$1,000+	$206	45.7 m3

Based on 200 m2 mixed garden (10 L/m2/week), 16-week season. Drip saves $46/year vs sprinklers - payback in ~4 years.

Watering frequency guide

Plant type	Times per week	L per session (100 m2)	Best time
Lawn (established)	2	250	Early morning (6-8 AM)
New lawn / seed	Daily	100-150	Morning + evening first 2 weeks
Vegetables	3-4	500-700	Morning (before heat)
Flower beds	2-3	300-500	Evening (6-8 PM)
Container plants	Daily	varies	Check soil moisture daily

Practical examples

Small lawn (50 m2, hose): 250 L/week, season: 4 m3. Actual: 5.7 m3 (70% eff.). Cost at $4.50/m3: $25.71/season. Installation: $30 for a hose.

Vegetable garden (80 m2, drip): 1600 L/week, season: 25.6 m3. Actual: 28.4 m3 (90% eff.). Cost: $127.80/season. Install: $280. Saves $49/year vs sprinklers.

Medium lawn (200 m2, sprinklers): 1000 L/week, season: 16 m3. Actual: 22.9 m3 (70% eff.). Cost: $103/season. Install: $500.

Large mixed garden (400 m2, automatic): 4000 L/week, season: 64 m3. Actual: 91.4 m3. Cost: $411/season. Install: $2,000+. The convenience justifies the price for large properties.

Drip vs sprinklers (200 m2 mixed): Sprinklers use 45.7 m3, drip uses 35.6 m3. That is 10.1 m3 less water per season - $46 saved per year. Drip costs $200 more to install but pays back in ~4 seasons.

FAQ

How much water does a lawn need per week?

An established lawn needs about 25 mm per week, which equals 5 liters per m2. A 200 m2 lawn: 1000 liters/week. Water deeply (15-20 min per zone) twice a week rather than lightly every day - deep watering encourages deeper roots.

Is drip irrigation worth the extra cost?

Yes, for vegetable beds and borders. Drip uses 35% less water than sprinklers (90% vs 70% efficiency). On a 200 m2 mixed garden at $4.50/m3, that saves about $46 per season. The extra $200 installation cost pays back in 4-5 years. For pure lawn areas, sprinklers are more practical.

When is the best time to water the garden?

Early morning (6-8 AM) is ideal - less evaporation and the lawn dries before evening (reducing fungal disease). Evening (6-8 PM) is second best. Never water during midday heat - up to 50% of water evaporates before reaching roots.

How much does an automatic sprinkler system cost?

For a 200 m2 garden: $1,000-1,500 including pop-up heads, pipes, controller and installation. A smart controller with rain sensor adds $150-400. Running cost: $100-200/season in water depending on your rate. The system typically lasts 10-15 years with minimal maintenance.

How often should I water vegetables?

3-4 times per week in summer, delivering 20 L per m2 per week total. Tomatoes and cucumbers are thirsty - they prefer deep watering every other day. Leafy greens (lettuce, spinach) prefer lighter, more frequent watering. Always water at the base, not on the leaves.

Do I need to winterize my irrigation system?

Yes, in any climate that freezes. Water left in pipes expands and cracks PVC fittings, drip lines and sprinkler heads. Blow out lines with compressed air (30-50 PSI) or drain manually. Close the supply valve and open all end caps. Do this before the first hard frost.

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