The latest articles on DEV Community by Yusuf Yusuf (@yusuf_invoiceluxe). https://dev.to/yusuf_invoiceluxe https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4211634%2F38d86864-7dcf-429a-aac1-0397ad3778af.png https://dev.to/yusuf_invoiceluxe en Yusuf Yusuf Tue, 27 Oct 2026 19:53:07 +0000 https://dev.to/yusuf_invoiceluxe/i-built-a-free-kdv-vat-calculator-pwa-22-languages-offline-no-signup-48gk https://dev.to/yusuf_invoiceluxe/i-built-a-free-kdv-vat-calculator-pwa-22-languages-offline-no-signup-48gk <p>I was tired of wrong KDV calculations in Turkey, so I built a free tool.</p> <p><strong>Live tool:</strong> <a href="https://www.invoiceluxe.com/tr/calculator.html" rel="noopener noreferrer">https://www.invoiceluxe.com/tr/calculator.html</a></p> <h3> The Problem </h3> <p>Most calculators do this wrong:</p> <p>600 TL including 20% KDV<br> Wrong: 600 - 20% = 480 TL<br> Correct: 600 / 1.20 = 500 TL net + 100 TL KDV</p> <p>My tool does it correctly.</p> <h3> Features </h3> <ul> <li>Add / Remove KDV (VAT) with %1, %8, %18 and custom rates</li> <li>Correct formula: net = gross / 1.20 for 20% case</li> <li>PWA - install on iPhone/Android, works offline, no App Store</li> <li>No signup, data stays on device</li> <li>International rates: Germany 19%, France 20%, Netherlands 21%</li> </ul> <h3> Why PWA? </h3> <p>I wanted a tool that works without App Store. It's a Progressive Web App with 25+ tools:</p> <ul> <li>Invoice Generator</li> <li>PDF Sign &amp; Create</li> <li>JPG to PDF</li> <li>QR Code, Password Generator etc.</li> </ul> <p>All 22 languages: TR, EN, DE, NL, FR, IT, ES, PT-BR, AR, JA, HI, ZH, RU...</p> <p><strong>TR version:</strong> <a href="https://www.invoiceluxe.com/tr/calculator.html" rel="noopener noreferrer">https://www.invoiceluxe.com/tr/calculator.html</a></p> <p>Built with Vanilla JS, offline-first.</p> <p>Open source feedback welcome!</p> <h1> webdev #productivity #javascript #opensource #pwa #vat #kdv #turkey #freelance </h1> pwa showdev tools webdev