External Wall Insulation Calculator
Complete take-off for insulation or renovation. Quantities, optional accessories, 1-click add to basket.
- UK-ready
- Real coverage
- NET prices (GBP)
How to Use the EWI Calculator (Step by Step)
A simple step-by-step process that gives you an accurate breakdown of all materials needed for your insulation or rendering project.
- 1. Enter wall area
Type in the total external wall area you plan to insulate or render.
- 2. Choose house type
Select detached, semi-detached, mid-terrace.
- 3. Select insulation scenario
- 4. Get instant results
The calculator displays required materials, quantities and estimated costs.
Add Your EWI materials to basket in One Click
Once the calculation is complete, you can add all required materials to your basket with a single click.
This includes boards, adhesives, mesh, primer, render, fixings and accessories – all matched to your project.
What is the EWI Calculator?
External Wall Insulation (EWI) requires several different materials – boards, adhesives, primers, mesh and silicone render.
For many homeowners, installers and self-builders, estimating the correct quantities can be difficult and time-consuming.
Our EWI Calculator provides an instant breakdown of all materials needed for your property, based on your total wall area, house type and chosen scenario.
The tool uses industry-standard consumption rates and real product performance to ensure accurate, realistic calculations.
solid brick walls
cavity walls
non-standard wall surfaces
detached / semi-detached / mid-terrace
- insulation, renovation and rendering scenarios
→ Learn more about solid wall insulation
→ Learn more about cavity wall insulation
- Included materials
EPS insulation boards (graphite)
Adhesive and basecoat materials
Reinforcement mesh
Silicone or acrylic render
Primer and finishing components
What does the EWI Calculator do?
The EWI Calculator instantly estimates all materials required for your external wall insulation project. Using your wall area, house type and chosen scenario, the tool provides a complete material breakdown and realistic consumption totals, ensuring accurate, ready-to-order calculations for any solid or cavity wall property.
It eliminates manual guesswork, speeds up project planning and helps homeowners, installers and contractors order the correct quantities the first time.
Key benefits of using EWI Calculator
- Accurate material quantities
Automatically calculates boards, adhesives, mesh, primer and render based on real UK consumption rates.
- Reduces material waste
Helps avoid overordering, saving money on every project.
- Fast and precise costs estimation
- Includes labour estimate
Quickly check professional installation costs.
Who is the EWI Calculator for?
Our External Wall Insulation Calculator is designed for:
Homeowners planning insulation or renovation
Installers and contractors needing fast material take-offs
Architects and surveyors preparing project specifications
Self-builders looking for accurate EWI material estimates
Trade customers pricing multiple properties or tender work
It provides reliable, ready-to-order calculations for both solid and cavity wall properties.
Why You can trust our EWI Calculator
Choosing the right amount of insulation materials requires accurate data, industry knowledge and real-world experience. Our EWI Calculator is built and continuously updated by insulation specialists at Penguins Builders Merchant , based on: 416 Ealing Rd, London, Wembley HA0 1JQ, United Kingdom
Verified consumption rates
All quantities are calculated using manufacturer-approved coverage rates for adhesives, basecoat, mesh, primers and silicone render.
Real project data
The calculator reflects real-world material usage from hundreds of external wall insulation installations across the UK.
Trade and installer experience
Our estimates are reviewed by certified EWI specialists who work daily with solid wall and cavity wall insulation systems.
Updated for current UK standards
Material quantities follow modern EWI specifications, U-value requirements and installation best practices.
Supported insulation thickness options
Different insulation thicknesses are available depending on your property type and energy-efficiency goals.
The EWI Calculator automatically adjusts material quantities and consumption rates based on the thickness you select.
- 50 mm – basic upgrade for small areas or outbuildings
- 70 mm – light insulation improvement for newer cavity-wall homes
- 100 mm – standard thickness for most UK solid-wall properties
- 120 mm – enhanced performance for achieving 2025+ insulation standards
- 150 mm – high-performance level for maximum heat retention and energy savings
Tip: Thicker insulation improves U-values but increases material quantities – the calculator updates this automatically to provide accurate estimates.
Not sure which thickness you should choose?
Check our full guide here:
👉 External Wall Insulation Thickness Guide UK
EWI Calculator - FAQ
How accurate is the calculator?
It uses UK-standard material consumption rates and is highly accurate for most property types.
Does the calculator include waste margin?
Can I use the calculator for render-only jobs?
Yes. Select the “Render only” scenario.
Is the calculator suitable for installers and builders?
Absolutely – it provides fast material take-offs for quotes and ordering.
Does it work for any wall type?
Yes – solid wall, cavity wall, blockwork, stone and mixed construction.
Ready to make your External Wall Insulation?
Get a quick estimate and a materials list with our free calculator, or talk to our team for expert advice and UK-wide delivery.
