What this site is
SavBuildTool is a set of small, focused tools for the calculations, conversions and everyday admin that come up in ordinary work and ordinary life — what a loan actually costs, what a monthly investment might grow into, whether a colour pair is readable, what changed between two JSON files, when a distributed team can actually meet, how many classes a student has left.
Each tool does one job. For most of them there is no dashboard to learn, no onboarding and no project to create first: you open the page, the tool is already there, and the result updates as you type. A few tools do keep your work for you, and those are described below.
What you can use now, and what needs an account
Almost everything here is an instant tool. You arrive from a search result, the tool is on the page, and you can use it, read the explanation and leave without ever being asked who you are. That is the default, and it is not going to change as the site grows. The site can also be installed to a home screen and keeps working offline for pages you have already opened, and that needs no account either.
A small number of tools need a free account, and only for a reason you can see. The Class & Attendance Tracker is one: a trainer and their student both have to open the same register from two different phones, and that is not something a browser can hold on its own. Favourites are the other half of it — starring a tool works immediately on the device you are using, and signing in is what carries that list to your phone.
New tools are added in both shapes. Some will need an account because they have to remember something for you; most will not. The page you land on always says which it is before you start, and nothing that works without an account will be moved behind one.
How the tools are built
Every calculator is written as a separate, tested piece of logic before it becomes a screen. The arithmetic is covered by automated tests that pin worked examples, boundary values and awkward inputs, so a change to the interface cannot quietly change an answer.
Where a tool follows a published standard or a public health guideline, the page says which one and links to it. The BMI calculator follows NICE and NHS adult guidance; the sleep planner cites the NHLBI and CDC; the contrast checker uses the WCAG thresholds rather than an approximation of them. Where a figure rests on an assumption — a rate, a fall-asleep allowance, an inflation number — the assumption is shown on screen and can be edited.
Worked examples in the explanatory text are checked against the tool itself rather than written from memory. When an input changes, the prose is re-checked with it.
What happens to what you type
The instant tools calculate in your browser. Loan figures, body measurements, sleep times, JSON documents and images are processed on your device: there is no upload endpoint behind them, and the numbers you enter are not sent to us, stored against you or attached to an account.
Three exceptions are worth stating plainly rather than burying. Some tools put their settings in the page address so a result can be shared as a link — that link is visible in your history and in ordinary server logs, and each of those pages says so. The to-do list deliberately saves your tasks in your own browser so they survive a refresh; they stay on that device until you delete them or clear the site's data. And the tools that need an account do keep what you enter on our servers, because that is the whole point of them: the Class & Attendance Tracker holds your students, their packages and their attendance, and your starred tools are kept against your account once you sign in.
Normal website activity still applies to the pages themselves. Analytics and advertising run only if you allow those cookie categories, and you can change that decision at any time on the Cookie Preferences page. The Privacy Policy sets out the whole picture.
Accessibility is part of the build, not a later pass
Every page carries an accessibility panel that adjusts text size, line spacing, contrast, motion, link underlining, the typeface and the pointer, and remembers the choice across the site. The controls are applied on the server, so a page arrives already in the settings you chose rather than rearranging itself after it loads.
Colour contrast is not left to judgement. The theme's colour pairings are checked automatically against the WCAG AA thresholds — body text, control boundaries and focus indicators — in every theme and section style the site uses, and a change that would drop a pairing below the threshold fails the build.
Status is never signalled by colour alone, every control is reachable with the keyboard, and results are readable as text rather than only as a chart.
How the site is paid for
The tools are free and advertising pays for them. Ads are kept to defined areas — a column beside the tool on wide screens, and below the tool elsewhere — and never inside the part of the page you are working in.
Advertising only loads if you have allowed the advertising cookie category. Decline it and the ad script is never requested at all, rather than being loaded and hidden. Nothing about a tool is held back behind a payment, and there is no paid tier that removes the limits.
What these tools are not
The calculators produce estimates from the numbers you give them. They are not financial, medical, legal or tax advice, and they cannot see your circumstances. A loan estimate is not a quote and will not match a lender's offer exactly; an investment projection assumes a constant return that real markets do not deliver; a health calculator is a screening aid, not a diagnosis.
Where a result carries that kind of weight, the page says so beside the number instead of hiding it in a footer. Confirm anything important with the organisation that will actually act on it.
Corrections and requests
If a tool gives an answer you believe is wrong, the Contact page is the fastest route and a correction is treated as a priority — a calculator that is quietly wrong is worse than one that is missing.
The same form takes suggestions for tools that do not exist yet, accessibility problems, and privacy requests. No account is needed to use it.
Common questions
Yes. Every published tool is free, with no trial and no paid tier — including the ones that ask you to sign in. Advertising pays for the site, and it loads only if you allow the advertising cookie category.