What Lots Of Calcs is, how it works, and what happens to anything you type into it.
What this is
Lots Of Calcs is a free collection of 49 calculators covering everyday sums, business and finance, home and DIY jobs, betting odds, and a few things built purely because they were interesting. There is no sign-up, no paywall, no trial, and nothing is held back behind an email address.
The aim is narrow and deliberate: each page should do one job properly, show its working, and explain the method rather than just producing a number. Most calculators online give you a figure and leave you to trust it. These ones show the formula, walk through a worked example with real numbers, and say where the result stops being reliable.
It started as somewhere to put a handful of tools worth having in one place, and grew from there. New calculators get added when a genuinely useful one comes to mind.
How it works
Every calculator is plain HTML, CSS and JavaScript. There are no frameworks, no build step, no third-party libraries and no external requests while you use them.
That matters for one reason above all: the sums happen on your own device. When you type a salary into the income tax bands, a price into the VAT calculator or a date into the birthday calculator, that value is handled entirely by your browser. It is never sent to a server, never written to a database, and never leaves your machine. Close the tab and it is gone.
A practical side effect: once a page has loaded, it keeps working offline.
The site is hosted on GitHub Pages, which serves static files. As with any web host, GitHub receives the ordinary request information a browser sends when fetching a page.
Analytics and cookies
The calculators send nothing anywhere, but the site as a whole is not invisible, and it would be misleading to imply otherwise. Lots Of Calcs uses Google Analytics 4 — but only if you allow it. Nothing analytics-related loads until you choose. Decline, or simply ignore the banner, and no analytics script is ever fetched, no request reaches Google, and no cookie is set. Accept, and it counts visits and records which calculators get used, which is what decides what gets built next.
What Google Analytics records:
Which pages are viewed, and in what order
Roughly where in the world the visit came from, at country or city level
Device type, browser and screen size
Which site or search engine you arrived from
How long you stayed
What it does not record: anything you type into a calculator. No figures, no dates, no salaries, no prices. Those values never reach the analytics script because they never leave your browser at all.
Google Analytics 4 does not store full IP addresses, and there is no advertising, remarketing, profiling or selling of data attached to any of this. Nothing here is used to identify you personally.
If you accept, Google Analytics sets two cookies in your browser — _ga, and a second one beginning _ga_ — which last about two years and hold a randomly generated identifier used to recognise a returning browser. Neither is set before you accept, and neither is essential to the calculators, which work perfectly well without them.
You can change your mind at any point, in either direction. Every page carries an Analytics on / off line in the footer with a Change button next to it, or use the button below. Switching it off also deletes the analytics cookies already in your browser rather than merely stopping new ones.
Independently of anything on this site, these will also stop it: Google's official Analytics Opt-out Browser Add-on, blocking cookies for this site in your browser settings, using private browsing, or running more or less any ad blocker or tracker blocker. None of it affects how the calculators behave.
One caveat worth stating, since this page is meant to be straight with you. Google Analytics is a Google product, and Google may use data passing through it for its own purposes as well as reporting it back to me. That is why consent is asked for here rather than relying on the exemption UK rules now allow for simple first-party visitor counting.
Accuracy, and what this site isn't
Every calculator is tested against worked examples before it goes live, and where a page relies on published figures — tax rates, surface gravities, energy prices — those are checked against primary sources rather than written from memory. Where a figure is a snapshot that will date, the page says when it was checked.
That said, a few honest limits are worth stating plainly:
Rates and thresholds change. Tax rates, VAT bands and similar figures move with budgets and legislation. Presets are a convenience and a starting point, not a guarantee that a rate still applies on the day you read it.
This is not professional advice. Nothing here is financial, tax, legal, medical or veterinary advice. The mortgage and loan calculators do not know your circumstances; the BMI calculator is a crude population measure and not a diagnosis; the pet age calculators are population averages, not a health assessment. For anything that matters, talk to someone qualified.
The betting calculators are arithmetic, not tips. They work out returns and stakes from odds you supply. They cannot tell you what will win, and no staking method changes the fact that the odds carry a margin in the bookmaker's favour. If gambling stops being fun, BeGambleAware is there.
Mistakes are possible. If you find one, it is worth telling me about — corrections get made.
Who makes it
Lots Of Calcs is built and maintained by Kai Jones. It is a personal project rather than a company, run in spare time, with no advertising and nothing for sale.
Suggestions for calculators worth adding are welcome, as are corrections.