Privacy Policy

Every calculator on 4calcs runs entirely in your browser using JavaScript. The numbers you type (your salary, home price, weight, or bill total) are never sent to or stored on our servers. When you close the tab, they are gone. “Copy result” uses your own clipboard and “Print / PDF” uses your browser’s print dialog.

We save three small preferences in your browser’s local storage: your light/dark theme, your privacy choices under the key 4calcs-privacy-v1 (ads consent and Do Not Sell / Share), and whether you dismissed the iOS “Add to Home Screen” tip. Our analytics keeps a few more small values on your device, described in section 4. We do not save your calculator inputs. You can clear all of this at any time from your browser settings.

The contact form is the one place where you send us information. When you submit it, your name, email address, subject and message go to our server and are delivered to our inbox by our email provider (Resend). We use them only to read and answer your message, and we keep them only as long as needed to do that.

To stop spam, the form carries a signed timestamp from our server and an ALTCHA check: a small proof-of-work puzzle your browser solves automatically. ALTCHA runs on our own server, so no third-party CAPTCHA service is contacted and no cookies are set.

Our server also uses your IP address to limit how many messages can be sent (five every ten minutes) and how often the ALTCHA puzzle can be requested. Before it is used, the IP is turned into a keyed hash (IPv6 addresses are grouped by network), so the address itself is not stored. The counter lives in server memory and, in production, in our rate-limit service (Upstash Redis), and expires within ten minutes. It is not used for anything else.

We use two analytics tools to count page views and see which calculators people find useful. Neither one ever receives your calculator inputs or anything you type into the contact form.

Vercel Web Analytics, built into our hosting provider (Vercel), is cookieless: it sets no cookies and does not track you across other websites. It records aggregated, anonymous page-view data, such as the page visited, the referring site, and your country, browser and device type. Its script is served from our own domain (4calcs.com), the data goes back to that same domain and is processed by Vercel. It may keep a single value in your browser’s local storage under the key __va_attribution.

Google Analytics 4 is a web analytics service provided by Google, which processes the data on our behalf. It helps us understand how visitors find and use 4calcs: which pages are viewed, how visits begin and how long they last, the referring site, your approximate location (country, region and city, derived from your IP address), your browser, device, operating system, screen size and language. We also send a few events about the 4calcs app: when it is installed, when it is opened as an installed app, and whether our “Install” prompt was accepted or dismissed. Google Analytics sets first-party cookies on 4calcs.com, such as _ga and _ga_K6W8GV8RYX, which hold a random identifier so repeat visits can be counted; they can last up to two years. Google Analytics 4 does not log or store IP addresses. We use this data only to understand and improve the site.

We use Google’s Consent Mode v2: in the EEA, the UK and Switzerland, analytics and ad storage default to denied until consent is updated (for example by Google’s consent message when ads are live); elsewhere they default to granted, except that a Global Privacy Control signal denies ad user data and ad personalization. Your local choices under 4calcs-privacy-v1 are also sent as Consent Mode updates.

You can learn more in how Google uses information from sites that use its services and in Google’s Privacy Policy. To opt out, block or delete cookies for 4calcs.com, or install the Google Analytics Opt-out Browser Add-on; every calculator keeps working either way. Apart from these two tools, we don’t use any other analytics or tracking scripts, and we don’t build profiles of visitors.

Some pages reserve clearly labeled spaces for ads, but no ad network is active today: no advertising code runs and no ad cookies are set. If we turn ads on, we will update this policy first. Ads will never appear before your result. US visitors will be able to Decline or opt out of sale/sharing; visitors in the EEA, UK and Switzerland will see Google’s consent message (Consent Mode v2 + Google CMP) before personalized ads.

4calcs needs no cookies to work. The only cookies on the site are the Google Analytics cookies described in section 4 (such as _ga); no ad cookies are set. You can block cookies entirely and every calculator will still work.

Like any website, the servers that deliver our pages may automatically log standard request data, such as IP address, browser type and the page requested, for security and reliability. These logs are not used for advertising.

We do not sell personal information. Under some US state privacy laws (such as California’s), using ad cookies for cross-context advertising can count as “sharing”. You can opt out below at any time; we also honor the Global Privacy Control signal automatically. When you opt out (or Decline ads), we store that choice in 4calcs-privacy-v1, update Consent Mode, and do not load our ad code in this browser.

4calcs is a general-audience site and is not directed at children under 13. We do not knowingly collect their personal information.

You can use 4calcs without an account; we don’t offer one. We may update this policy as the site changes; the date at the top shows the latest version. To ask a privacy question or request that we delete a message you sent us, email [email protected] or use the contact form.