Water Tank Size Calculator – Never Run Out of Water
Calculate the right cold water storage tank capacity (litres/gallons) for your home. Ensure adequate pressure for showers and avoid dry taps. 100% free, no sign-up.
Preview — get your tank size
What is the Water Tank Size Calculator?
An undersized cold water tank leads to empty cisterns, poor shower pressure, and running out of water during peak usage. An oversized tank wastes space and money. Our water tank size calculator uses bedrooms, bathrooms, and occupants to recommend the perfect capacity (litres). It's the essential plumbing calculator for system boiler homes, working alongside pipe flow calculator and water pipe sizing tools.
💧 Water Tank Sizing Tool
Enter your household details — get recommended cold water storage capacity
Smart Features for Accurate Sizing
Bedroom-Based Sizing
Core capacity calculation from bedrooms.
Bathroom Adjustment
More bathrooms = larger tank needed.
Occupant Factor
People count affects daily usage.
Peak Demand Logic
Refill rate based on incoming flow.
BS 6700 Compliant
Follows UK water regulations.
Mobile Ready
Use on-site during surveys.
Litres & Gallons
Dual unit display.
Plumbing Integration
Works with pipe flow calculator.
How It Works
Enter Bedrooms
Number of bedrooms
Add Bathrooms
Bathrooms & occupants
Select Usage
Peak period & property type
Get Results Instantly
Tank capacity in litres
Why Correct Water Tank Sizing Matters
Never Run Dry
Enough water for peak times.
95% Accuracy
Based on BS 6700 standards.
Saves Money
No oversized tank waste.
Avoid Low Pressure
Consistent shower performance.
Professional Results
Used by plumbers nationwide.
Who Uses Our Water Tank Size Calculator
🏠 Homeowners
- Check if your tank is undersized
- Plan new tank replacement
- Avoid running out of water
- Improve shower pressure
- Budget for tank upgrade
🔧 Plumbers
- Specify correct tank for jobs
- Integrate with pipe flow calculator
- Comply with Building Regulations
- Provide accurate quotes
- Avoid callbacks on low pressure
🏗️ Contractors
- New build tank specification
- Renovation project planning
- Social housing upgrades
- Building regs compliance
- Material ordering accuracy
🛠️ DIY Enthusiasts
- Plan home water system upgrades
- Understand tank sizing basics
- Compare tank options
- Budget for DIY installation
- Learn plumbing regulations
Why Choose Speedy Jet Plumbers?
We're not just a free tool provider — we're your local plumbing experts with 24/7 emergency response and thousands of satisfied customers.
Full certification
500+ 5-star reviews
60-minute arrival
Free quotes & surveys
Calculator + tank installation
💧 Need a New Cold Water Tank Installed?
Get a free site survey, professional tank sizing confirmation, and installation by experienced plumbers. We supply WRAS-approved tanks at trade prices.
⭐ Emergency service highlight — tank replacement, repairs, and pressure issues resolved 24/7 nationwide