About CalculatorCentrum
CalculatorCentrum is a collection of 113 free, focused calculators across 9 categories — electronics, IoT, physics, maths, finance, health, home and DIY, colour, and unit conversion. Each one does a single job, loads in well under a second, and shows the formula it used so you can check the method rather than trusting a number.
Who makes it
The site is built and maintained by Arthur Kingsfield, an electronics engineer working in PCB design and embedded systems. That background is the reason the site started where it did: the electronics and IoT calculators came first because they are the ones I needed myself and could not find in a form I trusted — trace current sizing, RC time constants, thermistor linearisation, RF link budgets. The other categories followed as the same approach turned out to apply just as well to physics, finance, and estimating materials for a job.
Where a calculator touches something outside my own field — the IV drip rate page, for instance, or the body-mass calculators — it sticks to arithmetic that is not in dispute, states its assumptions, and says plainly that it is a reference conversion rather than professional advice.
How the numbers are checked
Every formula on this site is verified when the site is built, not merely when it was written. Each calculator's maths lives in its own module with a set of assertions attached, and those assertions run as part of the build: if a constant is wrong or a formula is edited badly, the build fails and the change cannot be published.
This is not a formality — it catches real mistakes. Recent examples include a surface-gravity table that disagreed with published values for the gas giants (the quoted figures use each planet's equatorial radius, not its mean radius), a specific-heat field that kept its metric value when the units were switched, and a drag-coefficient entry whose mass and frontal area described two different objects. Each of those was caught before it reached the site. There is a fuller explanation on thehow we verify page.
How it works
The calculators are plain HTML and JavaScript with no framework and no backend, which is why they load quickly and keep working offline once the page is open. What that means for data is set out in theprivacy policy rather than advertised here.
What it deliberately isn't
These are working tools, not tutorials, and they are not a substitute for a qualified professional on anything that matters. Where a calculation relies on a standard or an approximation — IPC-2221 for PCB trace currents, IEC 60751 for platinum RTDs, the Mifflin–St Jeor equation for basal metabolic rate — the page names it, so you know both what was assumed and when to reach for a more detailed method. Structural, electrical, medical and financial decisions should be checked by someone qualified to sign off on them.
Corrections and requests
If a number looks wrong, I want to know. Corrections are taken seriously and are usually fixed within a day or two, along with a new assertion so the same mistake cannot come back. Requests for new calculators are welcome too, and a good few of the tools here exist because somebody asked. Either way, the contact page is the way to reach me.