--- title: "Glass Calculator — Performance to EN Standards | GT Glass" canonical_url: "https://gt.glass/calculator" last_updated: "2026-10-14T05:04:55.665Z" meta: author: "Glass Technique Ltd" description: "Free glass calculator: U-values, g-values, sound reduction, safety & fire ratings to EN 410, EN 673, EN 12758. Evidence-backed results." keywords: "glass supplier London, switchable glass, smart glass, security glass, fire-rated glass, acoustic glass, PDLC glass, mesh laminated glass, LED glass, Glass Technique Ltd" "og:description": "Calculate U-values, g-values, sound reduction, safety and fire ratings for any glass make-up. Every number from a published European standard." "og:title": "Glass Performance Calculator — EN Standards | GT Glass" "twitter:description": "Calculate U-values, g-values, sound reduction, safety and fire ratings for any glass make-up. Evidence-backed results." "twitter:title": "Glass Performance Calculator — EN Standards | GT Glass" --- Search products Calculator # Glass Performance Calculator U-values, g-values, sound reduction, safety and fire ratings for any glass make-up — to European standards, in seconds. Ask for a five-day trial Compare the plans ![The calculator with a double-glazed unit built: glass, argon gap, glass, with light, solar and thermal results and the spectral chart](https://gt.glass/images/calculator/plan_complete_calculator.jpg) What It Does ## **Build it** Describe the glass the way you would draw the section: outside face on the left, room side on the right. Ten tabs on the ribbon — glass, fire rated, laminates, interlayer, gap, smart, mesh, fabric, blind, polycarbonate — and coatings chosen on the pane. Single panes, laminates, double and triple units, laminated-in-laminate: any physically sensible combination. ## **Calculate it** Every calculation follows a published European standard rather than a rule of thumb, and the app tells you which standard produced each number. Light, thermal, acoustic, safety, fire, structural and durability — a full run for a unit takes about two seconds. ## **Declare it** A technical data sheet publishes everything the calculator knows about the make-up, each number labelled with how we know it. The Declaration of Performance never carries an estimate: a resistance class appears on it only where a laboratory certificate, or for some classes the maker's own published class for exactly that make-up, supports it. Any other class reads NPD. ![The calculator in the acoustic view, with the sound reduction tile brought forward](https://gt.glass/images/calculator/view_acoustic.jpg) Dashboard The build-up editor, the performance tiles and the spectral chart. Evidence System ## The evidence behind every number Every classification carries a label saying how strong the evidence behind it is. **Certified** A laboratory test certificate you have recorded covers the make-up being calculated. **Safe for:** Anything — contracts, insurance, a Declaration of Performance **Declared by maker** A maker publishes this class for its own product at exactly this make-up and interlayer. **Safe for:** Specifying, quoting, comparing — sound guidance, not a test of your product **Estimate** An engineering estimate: the make-up is at least as strong, layer by layer, as make-ups the makers publish, or the class follows a stated rule. The basis is shown with it. **Safe for:** Design decisions, before anyone pays for testing **No class** The evidence supports no class for this make-up. The reason is shown with it. **Safe for:** Knowing a class cannot be claimed, and why **Not assessed (NPD)** No performance determined — nothing was claimed. **Safe for:** Knowing where the gap is ### **NPD is a blank, not a zero, and certainly not a fail. ** Annealed glass showing NPD for the pendulum test is the correct answer — it is not a safety glass — and the app says so instead of inventing a class. ### **The quality of the input, too** Every product in the catalogue carries a data-quality grade — D (direct from the manufacturer's datasheet or a measured spectrum), C (calculated from public data), E (estimated), N (listed, data pending) — so you can see the quality of the input as well as the strength of the output. Standards ## Every number from a published standard Every calculation follows a published European standard, and the app tells you which standard produced each number. EN 410 (emissivity to EN 12898) ### **Light & Solar** Light transmittance Tv, reflectance (outside and inside faces), solar factor g, direct solar transmittance Te, UV transmittance, colour rendering Ra, colour (CIELAB). EN 673 (ISO 15099 available as alternative) ### **Thermal** U-value of the glazing, Ug. EN 12758 with ISO 717-1 ### **Acoustic** Rw, C and Ctr; laboratory-measured values used when a certificate exists. EN 12600 (pendulum), EN 356 (manual attack), EN 1063 (bullet), EN 13541 (blast) ### **Safety** Classes, each with its evidence label. EN 13501-1 (reaction), EN 13501-2 (resistance) ### **Fire** Reaction class always; resistance only when a certificate backs it. EN 16612 with EN 16613 interlayer stiffness ### **Structural** Strength and deflection checks for laminated and monolithic glass. EN 1279 series, EN ISO 12543-4 ### **Durability** Durability of insulating and laminated units. **Also covered:** Bird safety (ABC threat-factor method with LEED / NYC / CSA references), Classification without further testing (CWFT rules), total thickness, weight per m², surface temperatures, breakdown of absorbed solar energy per pane. Views ## Seven views of the same result They do not change any number. They bring forward the tiles that matter for that conversation and dim the rest, so a thermal discussion is not competing with a colour-rendering figure for attention. StandardOpticalThermalAcousticFireStructuralSafety Spectral Data ## The spectral chart — the fingerprint of a make-up A full-width chart under the build-up shows transmission, outside reflection and inside reflection across the wavelength range, with a readout that follows the cursor. A low-E coating shows as high transmission in the visible band and a sharp climb in reflection in the infrared — that shape is exactly what makes it a low-E coating. ![Spectral chart of a double-glazed unit: transmission and both reflections from 300 to 2500 nanometres](https://gt.glass/images/calculator/spectral_chart.jpg) Documents ## Two documents, two bars of evidence The calculator produces two outputs from the same make-up. Each number is labelled with how we know it. Technical data sheet ### **The full picture** Publishes everything the calculator knows about the make-up, each number labelled with how we know it. Available as a Basic and a Full report. Always calculated from measured product data: reaction to fire, Ug, the light and solar set, the sound reduction set. Declaration of Performance ### **The legal instrument** A legal instrument under the Construction Products Regulation, laid out in the regulation's Annex III structure. Fire, bullet and blast resistance are declared only from a laboratory certificate; burglar resistance and pendulum impact from a certificate or the maker's own published class for exactly that make-up. An estimate never appears on it and reads NPD. Documents are issued under the customer's own company details (letterhead from the account profile). Creating data sheets and Declarations of Performance is switched on for each customer by Glass Technique when the account is set up. ![The glass picker: choose a manufacturer, then family, product and thickness](https://gt.glass/images/calculator/picker_glass.jpg) Layer builder Manufacturer, family, product, thickness. ![The interlayer picker listing interlayer manufacturers](https://gt.glass/images/calculator/picker_interlayer.jpg) Interlayer selection PVB, ionoplast, EVA and TPU. ![Fire-rated glass searched by integrity, insulation, radiation, frame and pane size](https://gt.glass/images/calculator/picker_fire_rated.jpg) Fire-rated products Searched by what the opening needs. 6 mm toughened reads 1C2 in the app and NPD in the DoP, at the same time, from the same calculation. **Both are correct.** The data sheet shows the estimated class for design; the DoP declares only what the evidence proves. Lab Certificates ## Your test evidence, applied only where it belongs Record a test report once — class, reference, test house and, importantly, the make-up it was tested on — and from then on the app uses your certified value in place of its own estimate wherever that certificate genuinely applies. ### **Scoped, not sprayed** The engine compares the certified make-up against the build-up on screen before applying anything. An exact match is certified and declarable; anything else is set aside and a banner says which difference caused it (thickness, treatment, interlayer, layer count). A certificate for a 4/0.76/4 laminate can never certify 6 mm monolithic. ### **Extension certificates** If the document itself permits classification without further testing, tick it, and it reaches thicker-or-stronger make-ups — published as an estimate, and outranking generic brochure tables because a test you hold is better evidence about your product. Product Catalogue ## Over 7,000 catalogue entries from more than 130 manufacturers Float and low-iron glass, body-tinted glass, more than 2,000 coated panes, over 4,000 laminates by name, PVB / ionoplast / EVA / TPU interlayers, gases, smart glass, integral blinds, meshes, laminated fabrics, polycarbonate, bird-safe and fire-rated products. 7,000+Catalogue Entries 130+Manufacturers 2,000+Coated Panes 4,000+Laminates by Name Coated products are treated as what they are: one measured pane, not a clear pane plus an adjustment. Data comes from manufacturers' own datasheets and measured spectral files, the LBNL International Glazing Database of measured glazing products, and documents suppliers send us directly. Interlayer mechanics: a registry of stiffness-versus-time-and-temperature data for laminating interlayers, built from the manufacturers' own declarations. Every product entry records where its figures came from. Nothing in the catalogue is invented to fill a gap — where we do not have data, the product is marked "data pending" and the app refuses to calculate rather than guess. ### **The WORLD chip — only the suppliers you can actually buy from** Set the sales region and tick the manufacturers you want offered. Anything outside that scope does not appear in the pickers, so you cannot accidentally specify a product you cannot source. Starts on Glass Technique-approved suppliers; widen to the whole world when you want to. For Your Company ## Built for teams, not just individuals ### **Accounts for companies** Every account is opened by Glass Technique, by invitation. Manager and User roles: a Manager keeps the company's details, logo, certificates and the DoP header. Access can be suspended instantly. ### **Three plans** Essential, Professional and Complete — differing in which product ranges, manufacturers and calculation views are included. Compare the plans ### **Nothing hidden** Every product tab and every calculation view is shown on every plan. What your plan does not include carries a small padlock, and one click tells you how to add it. ### **Security and hosting** The calculation engine is never reachable from the browser; all traffic is encrypted; every account action is recorded in your own audit trail; hosted in the EU on dedicated servers with nightly backups. ### **Built-in help** Getting started, where numbers come from, data sheet vs DoP, why NPD is not a failure, coatings, a searchable Q&A, and a feedback form. ### **Support from people who know glass** Feedback and data requests are answered by Glass Technique's technical team; missing products become letters to the manufacturer. Plans ## Three plans, one calculator Every plan runs the same engine, the same standards and the same evidence labels. The plans differ in which product ranges, which manufacturers and which calculation views are included. Everyday glazing ### Essential For processors and glaziers working with standard glass, coatings, laminates built layer by layer and insulating units. - —Glass, coatings, interlayers and gas spaces - —Light, solar, thermal, sound and safety - —A shorter list of approved makers, with Glass Technique's own interlayers **Price:** contact us Specialist glazing ### Professional For contractors, façade engineers and specifiers who also answer for fire and structure. Everything in Essential, and - —Fire-rated glass, searched by what the opening needs - —Laminates by name, bird-safe glass and polycarbonate - —The Fire and Structural views - —Glass Technique-approved makers across glass, coatings and interlayers **Price:** contact us The whole catalogue ### Complete For companies that work across the whole range and buy worldwide. Everything in Professional, and - —Smart glass, mesh, laminated fabrics and integral blinds - —Every maker in the catalogue, worldwide **Price:** contact us | **What is included** | **Essential** | **Professional** | **Complete** | | --- | --- | --- | --- | | Product ranges | | | | | Glass Float, low-iron, tinted, patterned, coated panes | | | | | Coatings | | | | | Interlayers PVB, ionoplast, EVA, TPU | Glass Technique's range | | | | Gas spaces Air, argon, krypton, xenon | | | | | Laminates by name A named laminate inserts its whole make-up | | | | | Fire-rated glass Search by integrity, insulation, frame and size | | | | | Bird-safe glass | | | | | Polycarbonate | | | | | Smart glass Switchable glass, including BIPV | | | | | Mesh | | | | | Laminated fabrics | | | | | Integral blinds | | | | | Manufacturers | | | | | Makers offered in the pickers | A shorter list of approved makers | Glass Technique-approved makers | Every maker in the catalogue, worldwide | | Calculation views | | | | | Standard, Optical, Thermal EN 410, EN 673 | | | | | Acoustic EN 12758 with ISO 717-1 | | | | | Safety EN 12600, EN 356, EN 1063, EN 13541 | | | | | Fire EN 13501-1, EN 13501-2 | | | | | Structural EN 16612 with EN 16613 | | | | | Documents | | | | | Technical data sheet Basic and Full | Enabled per account | Enabled per account | Enabled per account | | Declaration of Performance | Enabled per account | Enabled per account | Enabled per account | | In every plan | | | | | An evidence label on every class | | | | | The spectral chart | | | | | Saved projects and the archive | | | | | Your own laboratory certificates | | | | | Your company's letterhead on documents | | | | | Manager and User roles, your own audit trail | | | | | Built-in help and support from Glass Technique | | | | | Price | | | | | Per year | Contact us | Contact us | Contact us | Data sheets and Declarations of Performance are switched on for each account by Glass Technique. Tell us what you need when you apply. Plans as set on the live calculator on 2 October 2026 — check against admin before publish. ### Nothing hidden, nothing in the way Whatever your plan does not include stays on the screen, grey, with a small padlock. Click it and a short message says what it is and how to reach us. Your own work carries on as before. Moving to a wider plan keeps your account, your projects and your certificates exactly as they are. The padlock and this message are live in the calculator since 2 October 2026. ![The calculator on the Complete plan](https://gt.glass/images/calculator/plan_complete_calculator.jpg) Complete — every tab and every view is open. Who It Is For ## Built for everyone who works with glass Glass processors Build make-ups, check performance figures, and generate datasheets and Declarations of Performance from one place. Glazing contractors Get U-values, g-values, sound reduction and safety classes for tenders and Building Control submissions. Architects Compare glass options with full performance data traceable to the standard that produced each number. Specifiers Find the right make-up and the right evidence level for every project stage — from early design to final declaration. Distributors Answer "what does this glass do?" quickly and accurately, with every figure backed by a standard. Built by Glass Technique ## Glass people built this for glass people Glass Technique Ltd has specified, processed and supplied architectural glass in London for years. The calculator encodes how the company actually answers customers' questions — from the make-up that fits the specification to the number that belongs on the Declaration of Performance. The team behind the calculator understands both the physics and the paperwork, because they do both every day. Questions ## Frequently asked questions Five-day trial ## Try it on your own glass for five days Ask for a trial and we will send you a personal link. Your five days start when you choose your password, not when the email arrives. - 1 **One person, in your own company's account.** The link can be opened for seven days. - 2 **The real calculator,** on the plan we agree with you, with every result in full on the screen. - 3 **Documents too.** Data sheets and Declarations of Performance can be produced; during the trial each page is marked "Trial — not for issue". - 4 **No surprises at the end.** We remind you the working day before. When the trial ends you are signed out and your work is kept. - 5 **Carry on where you stopped.** Take a plan and it is the same account, the same projects, the same password. One trial per email address. We will only use your details to answer your request about the calculator. No spam, no third-party sharing. [~~Privacy Policy~~](https://gt.glass/privacy). Glass Technique Ltd ## Questions about the calculator? [Email Us→](mailto:info@gt.glass) [ Contact Page](https://gt.glass/contact) info@gt.glass+44 (0)20 3838 030071–75 Shelton Street, London WC2H 9JQ