Privacy Policy

The short version

• The numbers you type into a calculator are not sent to us. They are used to compute a result and then discarded when you leave the page. There is no server-side log of calculator inputs, because they never reach a server.
• There are no accounts. You cannot sign up, so there is no profile, password or email address held for you.
• Two Google services do load on every page — Google Analytics and Google AdSense — and they set their own cookies and see your IP address. That is the main privacy consideration on this site, and it is described in detail below.

Calculator inputs and results

When a calculator page is first served, the calculation is run once on the server using the calculator’s own default values so the page arrives with a worked example already filled in. Those are our defaults, not your data.

Every calculation after that happens in your browser, in JavaScript downloaded to your device. When you change an input, nothing is transmitted: the figure is recalculated locally and the page updates. We therefore have no way to see what you calculated, and no ability to produce it if asked.

What is stored in your browser

The site uses your browser’s localStorage — storage that belongs to your device and is never uploaded — for a small number of preferences and conveniences:

• your light/dark theme choice, so the page does not flash on load;
• recently used and favourited calculators;
• your display preferences, such as currency and unit choices, so you do not have to reset them on each visit;
• anonymous usage counts that power the private usage summary page. These are read only by your own browser and are not reported to us.

You can erase all of it at any time by clearing site data for this domain in your browser settings. Nothing breaks permanently if you do; the site returns to its defaults.

Google Analytics

We use Google Analytics 4 to understand which calculators people use and which pages are broken or slow. It records page views and basic technical details such as approximate location (derived from IP address), device type, browser and referring site. It does not receive the values you enter into calculators.

Analytics is provided by Google and governed by Google’s Privacy Policy. You can prevent it from collecting anything by installing the Google Analytics opt-out browser add-on, or by blocking the script with a content blocker — the calculators work normally either way.

Google AdSense and advertising cookies

This site participates in Google AdSense. In plain terms, and as Google requires us to state:

• Third-party vendors, including Google, use cookies to serve ads based on your prior visits to this website or other websites.
• Google’s use of advertising cookies enables it and its partners to serve ads to you based on your visit to this site and/or other sites on the internet.
• You may opt out of personalised advertising by visiting Google Ads Settings.
• You can opt out of personalised advertising from many other vendors at www.aboutads.info.

Google explains how it uses the data it collects on sites like this one in How Google uses information from sites or apps that use its services, and how its advertising cookies work in Google’s advertising technologies policy.

Consent (EEA, UK and Switzerland)

For visitors in the EEA, the UK and Switzerland, consent for personalised advertising is collected by Google’s certified consent management platform, and until a choice is made advertising and analytics storage are treated as denied. You can change or withdraw your choice at any time with the Privacy settings link in the footer.

Opting out of personalised advertising does not remove ads; it makes them non-personalised. See the Cookie Policy for the specific cookie families involved.

Voice search

The optional voice search button uses your browser’s built-in Web Speech API. Depending on which browser you use, the audio may be sent to your browser vendor to produce a transcript — that is a function of your browser, not of this site, and it is covered by your browser vendor’s privacy policy. We receive only the resulting text, and match it against the calculator list locally.

The contact form

If you submit the contact form, the name, email address and message you provide are emailed to the site operator so that your message can be answered. They are used for that reply and nothing else — no marketing list, no onward sharing. This is the only feature on the site that deliberately transmits something you typed.

What we do not do

• We do not sell or rent personal information.
• We do not use the data for automated decision-making or profiling of our own.
• We do not ask for, or knowingly collect, information from children. This site is a general-audience reference tool and is not directed at children.

Your rights

Depending on where you live, you may have the right to ask what personal data is held about you, to have it corrected or erased, and to object to its processing.

It is worth being precise about what that means here. Because calculator inputs never reach us and there are no accounts, in the ordinary case we hold no personal data about you at all, and an access request would correctly be answered “none”. The exceptions are the contents of a contact-form message you chose to send us, and the data held by Google in its own capacity as a provider of Analytics and AdSense.

For the Google-held data, the controls are Google’s own: use the opt-out links above, and Google’s data and privacy settings for data tied to a Google Account.

For anything we hold, use the contact form and say that your message is a data-protection request, so it can be routed correctly.

Changes to this policy

When this policy changes, the “last reviewed” date at the top of the page changes with it. That date is set by hand when the text is actually re-read, so it means what it says rather than tracking the most recent deployment.