UK PART G WATER EFFICIENCY CALCULATOR

Part G water calculations made simple.

Calculate your property's water consumption online and produce a professional Building Control report without the complicated spreadsheets.

Start Your Calculation See How It Works
✓ No technical knowledge needed ✓ No account needed to start ✓ Single and multiple dwellings
EXAMPLE RESULT

Your water calculation

Pass
109.6 litres per person per day
Selected target 125 litres
PDF
Building Control Report Ready to download
✓
HOW IT WORKS

Your calculation in three simple steps

Answer a few straightforward questions about the property and its water fittings. We handle the calculation and report.

1

Tell us about the property

Choose a single dwelling or multi-plot development and enter the basic project details.

2

Add the water fittings

Enter the quantities, flow rates and capacities using our simple guided questions.

3

Get your result and report

See whether the property passes and download your professional Building Control report.

Start Your Calculation
WHAT YOU GET

A report Building Control can check in minutes

Every passing calculation can be issued as a professional PDF package, ready to upload to your Building Control body or approved inspector.

  • 1
    Water Efficiency ReportA one-page summary with the property, the requirement selected (125 or 110 litres) and the final litres per person per day.
  • 2
    Part G Calculation ScheduleEvery fitting and appliance, its flow rate or capacity, the Appendix A factors and each contribution, so the working can be followed line by line.
  • ✓
    Verification codeEach document carries a unique code and link, so Building Control can confirm it is genuine and unchanged.
  • ◫
    Your own branding if you want itArchitects and developers can add their company name and logo to the reports.
Approved Document G methodThe full Appendix A calculation, using the official factors and appliance defaults.
Checked twiceYour browser and our server both calculate the result. If they ever disagree, no report is issued.
Pass before you payTry different fittings as many times as you like. You only pay once your specification passes.
Building regulations specialistsOperated by One Stop Consult Ltd, a UK building regulations consultancy.
SIMPLE PRICING

Calculate for free. Pay only for the report.

Check whether your specification passes Part G before spending anything. Purchase the professional report only when you’re ready.

CALCULATION
Free

Use the complete calculator and check your result without payment.

  • Single and multiple dwellings
  • Instant PASS or FAIL result
  • Guidance for improving failed results
  • No account required to start
Check If Your Property Passes
BUILDING CONTROL REPORT FIRST PLOT
£20 + VAT

£24 including VAT

  • Professional PDF report
  • Detailed calculation schedule
  • Ready for Building Control submission
  • Instant download after purchase
Each additional plot £10 + VAT
Start Your Free Calculation

You’ll see your calculated result before being asked to purchase a report.

COMMERCIAL & NON-DOMESTIC

Need a commercial water efficiency calculation?

Offices, schools, retail, hotels and mixed-use schemes, including BREEAM Wat 01 water consumption. Send us your drawings for a fixed-fee quote.

Commercial calculations →
COMMON QUESTIONS

Everything you need to know

Straightforward answers about using the calculator and purchasing your Building Control report.

Is the water calculation genuinely free?

Yes. You can complete the calculator, see your estimated litres-per-person-per-day result and check whether the property passes without making a payment. You only pay if you choose to purchase the professional Building Control report.

What information will I need?

You’ll need basic information about the property’s toilets, wash-hand basins, kitchen and utility sinks, showers and baths. The calculator explains exactly what figures to enter at each step.

What happens if my property fails?

You can change the proposed fitting specifications and recalculate as many times as required for free. The calculator highlights the areas affecting the result and provides practical improvement suggestions.

Can I calculate multiple dwellings or plots?

Yes. You can set up multiple plots and different house types within the same development. The first report costs £20 + VAT, with each additional plot report costing £10 + VAT.

Is the report suitable for Building Control?

The report follows the Approved Document G water-efficiency calculation methodology and includes a detailed calculation schedule suitable for submission to Building Control. Final acceptance remains with the relevant Building Control body.

Do I need to create an account?

You don’t need an account to start or complete the free calculation. Account details are only required when purchasing a report, allowing you to securely access your completed reports afterwards.

Is this a water meter calculator?

No. It is a Part G water efficiency calculator that shows Building Control how much water a new home is designed to use. To find out whether a water meter would lower your household bills, use the Consumer Council for Water calculator or ask your water company.

Do you do commercial water efficiency calculations?

Yes. For offices, schools, retail, hotels and mixed-use schemes, including BREEAM Wat 01 water consumption, see our commercial water efficiency calculations page for a fixed-fee quote.

GUIDES

Part G water efficiency, explained

Practical guides to the targets, the calculation and getting it signed off.

THE BASICSPart G water calculations explainedWhat the calculation is, who needs one and how the 125 and 110 litre limits work.Read guide → TARGETS110 vs 125 litres: which target applies?How to tell from your planning permission which limit you need to meet.Read guide → FIXING A FAILHow to get a failed calculation to passThe fittings that move the result most, with worked figures.Read guide → SUBMISSIONWhat to submit to Building ControlWhat surveyors check, when it is due and what to do if fittings change.Read guide → CONVERSIONSConversions and change of useBarns, offices, shops and flat conversions: when a calculation is needed.Read guide → WATER REUSEGreywater and rainwater in Part GHow reuse systems and water softeners are counted in the calculation.Read guide → COMMERCIALCommercial water efficiency calculationsOffices, schools, retail and mixed-use schemes, including BREEAM Wat 01.Find out more → FREE TOOLWater efficiency calculatorCheck a new home against 125 or 110 litres per person per day in minutes.Open calculator → REPORTSBuilding Control report pricingFree to calculate. Reports from £20 + VAT, £10 + VAT for each extra plot.See pricing →
FREE TO CALCULATE

Ready to check your property?

Get an instant Part G result without payment. Only purchase the Building Control report if you need it.

Start Your Free Calculation No account or payment required to start
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