Rainfall Calculator
Calculate rainfall volume, water collection, and catchment area for any precipitation event
Rainfall Water Collection Calculator
The surface area that collects rainfall
The height of rain that falls (precipitation depth)
Rainfall Calculation Results
Formula: Vrainfall = drainfall × Acatchment
Where: V = Volume, d = Depth, A = Area
Quick Examples
Example Calculation
Backyard Water Collection
Scenario: Collecting rainwater from a 50m² backyard
Rainfall: 5cm (50mm) of rain in one day
Calculation: 50 m² × 0.05 m = 2.5 m³ = 2,500 liters
Weight: 2,500 kg of water collected
Real-World Applications
• Rainwater Harvesting: Calculate storage tank requirements
• Flood Management: Estimate runoff volumes
• Agriculture: Plan irrigation and water storage
• Construction: Design drainage systems
Rainfall Facts
Global Average
~990mm per year
Worldwide precipitation
Record Rainfall
1,825mm in 24 hours
Reunion Island, 1966
Water Weight
1 liter = 1 kilogram
At standard conditions
Calculation Tips
Measure catchment area accurately for best results
Account for roof material efficiency (90-95% typical)
Consider first flush diverters for cleaner collection
Plan storage capacity for irregular rainfall patterns
Understanding Rainfall Calculations
What is Rainfall Volume?
Rainfall volume is the total amount of water that falls on a given area during a precipitation event. It's calculated by multiplying the rainfall depth (how deep the water would be if it didn't run off) by the catchment area (the surface area collecting the rain).
Why Calculate Rainfall Volume?
- •Design rainwater harvesting systems
- •Plan drainage and flood management
- •Estimate water availability for agriculture
- •Calculate runoff for urban planning
Calculation Formula
Vrainfall = drainfall × Acatchment
- Vrainfall: Total water volume collected
- drainfall: Depth of rainfall (precipitation)
- Acatchment: Area of the collecting surface
Remember: Real collection efficiency is typically 85-95% due to splash, evaporation, and absorption losses.
The Water Cycle and Rainfall
☀️ Evaporation
Solar energy heats surface water, turning it into water vapor
☁️ Condensation
Water vapor rises, cools, and forms clouds at high altitudes
🌧️ Precipitation
Water droplets combine and fall as rain, snow, or other precipitation