Water Tank Size Calculator

Water tank sizing ensures you have enough storage for your needs between refills or rainy periods.

Required Capacity = Daily Usage × Days of Storage

Unit conversions:

• 1 gallon = 3.78541 liters
• 1 liter = 0.264172 gallons
• 1 cubic foot = 7.48 gallons = 28.32 liters

Typical daily water usage for gardens:

• Small garden (100 sq ft): 5–15 gallons (19–57 L)
• Medium garden (500 sq ft): 25–50 gallons (95–189 L)
• Large garden (1,000 sq ft): 50–100 gallons (189–378 L)
• Greenhouse: 10–30 gallons (38–114 L)
• Lawn irrigation (1,000 sq ft): 60–80 gallons (227–303 L)

Household water usage (non-garden):

• Per person per day: 50–100 gallons (189–378 L)
• Toilet flush: 1.6 gallons (6 L)
• Shower (10 min): 20 gallons (76 L)

Storage recommendations:

• Dry climate: 14–30 days of storage
• Moderate climate: 7–14 days of storage
• Wet climate: 3–7 days of storage

Common tank sizes:

• Rain barrel: 50–100 gallons (190–380 L)
• Small tank: 250–500 gallons (950–1,900 L)
• Medium tank: 1,000–2,500 gallons (3,800–9,500 L)
• Large tank: 5,000–10,000 gallons (19,000–38,000 L)