This translation is provided for convenience only. If there is any difference between this translation and the English version, the English version prevails.
1. Data controller
The data controller is MARFEN-MAHMUT TARI, sole proprietor trading as CalcHandbook, Türkiye. Contact: support@calchandbook.com. This policy is written to meet the Turkish Personal Data Protection Law No. 6698 (KVKK) and the EU/UK General Data Protection Regulation (GDPR).
2. Calculations stay in your browser
The calculators run entirely in your browser. The numbers you type, and the project, subject and “prepared by” fields on reports, are not sent to our servers. Some of them are kept in your browser’s local storage so the report page and your preferences work; you can clear them at any time by clearing site data in your browser.
3. What we collect
- Technical data: when you visit the site, our hosting provider processes standard request data (IP address, browser type, requested page, time) to deliver pages, keep the service secure and prevent abuse.
- Purchase data: when you buy a plan, Paddle.com (our Merchant of Record) collects your name, e-mail, billing country and payment details. We receive your e-mail, plan, country and transaction status. We never see or store your full card details.
- Account data: if you create an account, we store your e-mail address, plan and subscription status so we can give you access.
- Messages: if you e-mail us, we keep the correspondence to answer you.
4. Why we use it (legal bases)
- To provide the Service and your paid plan — performance of a contract.
- To keep the site secure and working — our legitimate interests.
- To keep invoices and transaction records — legal obligations.
- To send service e-mails about your account, renewals and important changes — performance of a contract. We do not send marketing e-mails without your consent.
5. Who we share it with
We do not sell personal data. We share it only with service providers who process it on our behalf:
- Cloudflare, Inc. — hosting, content delivery, security and e-mail forwarding.
- Paddle.com Market Ltd — checkout, payments, invoicing and tax (see Paddle’s privacy notice).
These providers may process data outside Türkiye and the EU, including in the United States. Where required, transfers rely on appropriate safeguards such as standard contractual clauses.
6. Cookies and local storage
We do not use advertising or cross-site tracking cookies. We use browser local storage for your report fields and preferences, and — once you sign in — a strictly necessary cookie to keep you logged in. Paddle’s checkout may set its own strictly necessary cookies during payment.
7. How long we keep it
- Account data: while your account is active, and up to 12 months after closure.
- Transaction records: as long as tax and commercial law requires (up to 10 years).
- Server request logs: kept by our hosting provider for a short period, typically no more than 30 days.
8. Your rights
Under KVKK (Article 11) and the GDPR you can ask to access, correct, delete or export your personal data, object to or restrict certain processing, and withdraw consent where processing is based on consent. E-mail support@calchandbook.com; we reply within 30 days. You may also complain to the Turkish Personal Data Protection Authority (KVKK) or your local data protection authority.
9. Children
The Service is intended for engineering students and professionals and is not directed at children under 16.
10. Changes
We will post any changes on this page and update the date above. Material changes will be announced on the site or by e-mail.