What this site is
The Big Bin Toolbox is a collection of 14 small, single-purpose web tools — calculators, generators, converters and text utilities — that do one job each and do it immediately. You open a page, the tool is already there, and you get an answer. There is no account, no free trial, no "sign up to see your result", and no ten-step wizard in front of a calculation that takes one line of arithmetic.
That sounds like a low bar. It isn't, apparently. Most of the tools I was replacing when I built this made me dismiss a cookie wall, close a newsletter modal, scroll past six hundred words of keyword filler, and then wait for a page reload to see a number my phone could have computed instantly. The whole point of this site is that the tool is the first thing on the page and the explanation comes after it, for the people who want it.
Who builds it
One person. Me. I'm an independent developer, and The Big Bin Toolbox is a side project I build and maintain on my own — the code, the interface copy, the formulas behind each calculator, the writing in the guides, and the server it runs on. There's no team, no company, and no investor behind it, and I'd rather say that plainly than pad the page with a fictional "we".
Practically, that means a few things worth knowing. Fixes and new tools arrive when I have time, not on a roadmap. If you email me, I'm the one who reads it. And when a tool here gets something wrong, there's exactly one person to tell — which I'd argue makes it more likely to get fixed than a form that disappears into a support queue.
It also means I'm careful about what I claim. The health-related tools on this site — BMI, period tracking, due dates, sleep cycles — implement published, widely-used formulas, and every one of them says on the page what it can and can't tell you. I'm a developer, not a clinician, and the tools are written to be honest about that rather than to sound authoritative. If you want the details of where each formula comes from and how it's checked, that's all written up on the methodology page.
Everything runs in your browser
This is the part I care most about. Every tool on this site is plain HTML, CSS and JavaScript that executes on your device. Your inputs are never transmitted anywhere, because there is no backend to transmit them to — the pages are static files served by a web server, and the arithmetic happens in the tab you have open.
Concretely: the passwords generated by the Password Generator are produced by your browser's own cryptographic random number generator and never leave the page. The dates you enter into the Period Calculator or the Due Date Calculator — which are, for a lot of people, some of the most sensitive information they'd ever type into a website — are held in memory and discarded when you close the tab. The JSON you paste into the JSON Formatter is parsed locally, which matters a great deal if it happens to contain an API key.
You do not have to take my word for this. Open your browser's developer tools, switch to the network tab, and use any tool on the site. You'll see the page load and the ad script load, and you will not see your data go anywhere. The one deliberate exception is the Word Unscrambler, which downloads a word list for the language you pick — it fetches the dictionary, not your letters.
How the tools fit together
The tools aren't a random pile. Several of them were built as sets, because the questions people actually have tend to span more than one calculation.
- Trying to conceive, and pregnancy. The Period Calculator finds your fertile window; the Due Date Calculator takes it from a positive test through trimester milestones; the Age Calculator counts your baby's age in weeks and months afterwards, which is the unit every pediatric appointment uses for the first two years.
- Buying a home. The Mortgage Calculator handles payments and amortisation; the Unit Converter deals with the square-feet-versus-square-metres problem that comes up constantly in listings; the Age Calculator answers "how old will I be when this is paid off", which is a question a surprising number of people only think to ask afterwards.
- Shipping a website or a design. The Color Picker builds the palette and checks contrast, Lorem Ipsum fills the layout, the JSON Formatter untangles the API response, the Word Counter checks that the meta description fits, and the QR Code Generator turns the finished URL into something printable.
- Sorting out your accounts and your sleep. The Password Generator makes credentials worth using, and the QR Code Generator hands out your WiFi without reading the password aloud. The Sleep Calculator and the BMI Calculator cover the two things people most often try to fix in the same week.
Each tool page ends with the specific tools that pair with it, and the guides walk through these combinations properly with worked examples.
How it pays for itself
Advertising, and nothing else. There's no paid tier, no data brokerage, and nothing about you is sold — there's nothing to sell, since the tools don't collect anything. A domain and a server cost money every month, and ads are how that gets covered without putting a tool behind a payment form.
What that buys you is a set of rules I hold myself to: no ad appears before the tool, nothing pops up over what you're doing, nothing auto-plays sound, and the layout doesn't shift under your cursor because a banner loaded late. If a placement would make a tool worse to use, it doesn't go in. That's the whole deal — the tools stay free, and in exchange the ads stay out of your way.
What this site deliberately doesn't do
- No accounts. There is nothing to sign up for and no password of mine for you to reuse. Nothing is saved between visits.
- No analytics on your inputs. I don't log what you calculate, generate, unscramble or paste.
- No medical, legal or financial advice. The calculators do arithmetic on numbers you supply. Interpreting the result for your situation is a conversation for a doctor, a lawyer or a lender, and every relevant page says so.
- No fake urgency. No countdown timers, no "3 people are viewing this", no invented scarcity.
Get in touch
Bug reports, tool requests, corrections to a formula, or anything else — the contact page has the details. Corrections are genuinely welcome; if a calculator here disagrees with a source you trust, I want to know which one and why.