Privacy Policy

Last updated: 17 August 2026

Spring Calculator Professional (springcalculator.com) is operated by the Institute of Spring Technology ("IST", "we"). This policy explains what personal data we hold when you use the service and what we do with it. We keep it deliberately short and specific.

What we collect

• Account details — your email address, a securely hashed password (we can never see the password itself), and any company details you choose to enter.
• Your designs — the spring designs you save are stored in a database private to your account.
• Usage records — sign-ins and design activity (designs created, opened, saved and edited), together with a per-browser session identifier and a one-way hashed form of your IP address. We use these to operate and improve the service and to detect sharing of a single account. We do not store your raw IP address against activity records.
• Messages — anything you send us via the contact form or by email.

Payments

Subscription payments are processed by Stripe. Your card details are entered on Stripe's secure checkout and go directly to Stripe — they never touch our servers and we cannot see them. We hold your subscription status and billing history (which spring types, renewal dates, invoices), and Stripe acts as an independent controller of the payment data it processes.

Email

We send transactional email only — subscription confirmations, renewal reminders and similar — delivered via Amazon SES. We don't send marketing email from the service, and we never sell or share your address.

Cookies

The application uses a single essential cookie that keeps you signed in. There are no advertising cookies and no third-party analytics or tracking scripts.

Design share links

When you create a share link for a design, anyone who has that link can view the shared snapshot without signing in, until the link expires or you revoke it from your Designs page. Choose what you share accordingly — the link itself is the only key.

Where your data lives

The service is hosted on Microsoft Azure in the West Europe region. Your account data is backed up automatically to separate Azure storage; superseded backup copies are retained on a rolling basis (approximately 90 days) and then deleted automatically.

Retention and deletion

We keep your data while your account is active. If you ask us to delete your account we remove your login, your saved designs and your account's data files; records we are legally required to keep (such as invoicing history) are retained for the statutory period. Backup copies of deleted data expire on the rolling backup cycle described above.

Your rights

Under UK data protection law you can ask us for a copy of your personal data, ask us to correct or delete it, or object to or restrict our use of it. Email support@ist.org.uk and we'll respond promptly. You also have the right to complain to the Information Commissioner's Office (ico.org.uk).

Changes

If we change this policy we'll update this page and the date above; material changes will be flagged to signed-in users.

Questions? Contact us or email support@ist.org.uk.