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Harrington Tools
12 free tools to help you plan your window project. From cost calculators and grant checkers to energy savings estimators and planning permission guidance — everything you need to make informed decisions.
Featured Calculators
Our flagship calculator tools with detailed cost estimation and investment analysis.
Window and Door Calculator Tools
Window Price Calculator
Use our window price calculator to instantly estimate replacement costs. This window cost estimator considers double glazed windows, window type, style, materials, and size for an accurate budget.
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Window U-Value Calculator
Unlock your home's energy efficiency with the Harrington Windows U-Value Calculator. Evaluate window performance, save on energy bills, and enhance comfort. Ideal for homeowners and builders seeking sustainable solutions.
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Window Investment Calculator
Estimate how upgrading your windows boosts home value, saves energy, and delivers strong ROI. Plan smarter renovations and unlock your property's potential today.
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Sliding Door Cost Calculator
Discover the cost of sliding glass doors, patio doors, and replacements with our Sliding Door Cost Calculator UK. Easily calculate prices for materials, glazing options, and installation.
Try NowInteractive Tools & Checkers
Our newest suite of interactive tools to help you with grants, planning, energy efficiency and finding the right windows for your home.
Window Grants Checker
Check your eligibility for UK government grants including ECO4, Warm Homes Plan, and LA Flex. Find out if you qualify for free or subsidised replacements.
Window Style Finder
Take our 6-question interactive quiz to discover the perfect window style for your home. Matches your property era, priorities, budget, and taste.
Double Glazing Calculator
Instant double glazing cost estimates by material, glazing type, size and quantity. Covers uPVC, aluminium and timber with 2026 UK pricing.
Calculate CostPlanning Permission Checker
Find out if you need planning permission. Covers listed buildings, conservation areas, building regulations, and FENSA requirements.
Check NowEPC Rating Calculator
See how upgrading windows could improve your EPC rating. Essential for landlords meeting MEES regulations and homeowners boosting property value.
Estimate ImpactEnergy Savings Calculator
Calculate exactly how much you could save on energy bills by upgrading your windows. Factors in property type, heating system, and current glazing.
Calculate SavingsCondensation Calculator
Check your condensation risk based on room temperature, humidity, and window type. Uses dew point science with tailored prevention recommendations.
Check RiskWindow Measurement Guide
Interactive step-by-step guide to measuring windows accurately for replacement. Includes SVG diagrams, squareness checks, and standard UK size matching.
Start MeasuringWhy Use Our Calculators?
Accurate Estimates
Get precise cost estimates based on your specific requirements and preferences.
Energy Insights
Understand potential energy savings and environmental impact of your window choices.
Investment Planning
Make informed decisions about your property improvements with ROI calculations.
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Limited Time Offer
Get 20% Off Your First Project with Harrington
Take advantage of our exclusive calculator discount and save 20% on your first window installation. Our expert team will help transform your vision into reality with premium quality windows that enhance both aesthetics and energy efficiency.
Get Your 20% OffLimited time offer, applicable to new customers only