--- title: "Glass Calculator — Performance to EN Standards | GT Glass" canonical_url: "https://gt.glass/calculator" last_updated: "2026-09-24T03:21:45.635Z" 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. Register for Early Access ![Glass Technique Calculator dashboard showing glass build-up editor with performance metrics](https://gt.glass/images/calculator/calculator-dahboard-screenshot.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. Eight layer types — glass, coating, interlayer, gap, smart, mesh, blind, polycarbonate — picked from a ribbon. 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 datasheet publishes everything the calculator knows about the make-up, each number labelled with how we know it. The Declaration of Performance declares only what a laboratory certificate supports; everything else reads NPD. ![Glass performance calculator dashboard showing 8-layer glass build-up with U-value, g-value and acoustic metrics](https://gt.glass/images/calculator/calculator-dahboard-screenshot.jpg) Dashboard 8-layer glass build-up editor with real-time performance calculations. Evidence System ## The evidence behind every number Every classification carries a badge saying how strong the evidence behind it is. **Certified** A laboratory tested this exact make-up and the report is recorded. **Safe for:** Anything — contracts, insurance, a Declaration of Performance **Tabulated** Matched to a checked reference document, e.g. a manufacturer's published table. **Safe for:** Specifying, quoting, comparing — not declaring **Predicted (CWFT)** Inside the envelope of a real test certificate under the equal-or-better rule. **Safe for:** Design decisions with more confidence than a plain prediction **Predicted** Worked out from physics and the rules of the standard. **Safe for:** Early design; sizing up options before anyone pays for testing **Not Assessed (NPD)** No Performance Declared — 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. 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 badge. 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. ![Glass performance calculation results with EN standard references and evidence quality badges](https://gt.glass/images/calculator/calculator-result-screenshot1.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 Datasheet ### **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. It declares only what a laboratory certificate supports; everything else reads NPD. Documents are issued under the customer's own company details (letterhead from the account profile). ![Adding a glass pane layer in the calculator build-up editor](https://gt.glass/images/calculator/add-layaer-glass.jpg) Layer Builder Add glass panes to your build-up with a single tap. ![Selecting PVB, ionoplast or EVA interlayer in the glass calculator](https://gt.glass/images/calculator/add-layer-interlayer.jpg) Interlayer Selection Choose from PVB, ionoplast, EVA and TPU interlayers. ![Selecting fire-rated glass with integrity and insulation ratings in the calculator](https://gt.glass/images/calculator/add-layer-fire-rated-glass.jpg) Fire-Rated Products Select fire-rated glass with integrity and insulation ratings. 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 datasheet shows the predicted class for design; the DoP declares only what the certificate 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 prediction 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 predicted (CWFT), and outranking generic brochure tables because a test you hold is better evidence about your product. Product Catalogue ## About 1,300 products from over 100 manufacturers Float and low-iron glass, body-tinted glass, about 480 coated products, PVB / ionoplast / EVA / TPU interlayers, gases, spacers, sealants, smart glass, BIPV, integral blinds, meshes, polycarbonate, bird-safe and fire-rated products. \~1,300Products 19Categories 100+Manufacturers \~480Coated Products Coated products are treated as what they are: one measured pane, not a clear pane plus a 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** Invitation-only sign-up. Manager and User roles; managers control who on their team can record certificates and issue DoPs; access can be suspended instantly. ### **Three plans** Essential, Professional and Complete — differing in which product families, manufacturers and calculation modules are included. Declarations of Performance are in every tier. ### **Admin controls** Choose which manufacturers are offered by default, which are available, which are hidden, and which regions each sells into — without ever editing the product data itself. ### **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, datasheet 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. 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 Early Access ## Be first to calculate The Glass Technique Calculator is in final development. Register your interest and we will let you know the moment it is ready. We will only use your details to notify you 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)