knowfromus.com is a collection of free calculators, built and maintained by one person. My name is Ranvir Singh. I have worked in digital marketing since 2012, mostly on search and paid advertising for small businesses, and I built this site because I kept needing tools like these and kept being disappointed by the ones I found.
Why This Site Exists
Most online calculators give you a number and nothing else. You type in your figures, a total appears, and you have no idea whether to trust it. There is no explanation of the formula, no statement of what the tool assumed on your behalf, and often no way to tell when the page was last looked at.
That is a problem when the answer matters. Order too little concrete and the pour fails. Compare two loan quotes on figures that are not comparable and you pay for it every month for three years.
So every tool here is built to show its working. The page under the calculator explains the formula, states the assumptions, and tells you where the figures came from. If the result depends on something that varies, the page says so rather than quietly picking a value for you.
How the Calculators Are Built
Every tool is written from scratch for this site. None of them are bought templates or embedded third-party widgets, which is why they all work the same way and none of them ask you for an email address before showing a result.
- The arithmetic is tested before a calculator goes live, with worked examples checked by hand against the tool’s output.
- Constants that come from a standard or an agency, such as material densities, mortar coverage, or payroll tax rates, are checked against the source rather than recalled. Where a page relies on one, it links to it.
- Nothing runs on your data. The calculators work entirely in your browser, nothing you type is sent anywhere or stored, and there are no accounts.
Prices Come From You, Not From Us
You will notice that none of the tools here quote you a price for anything. That is deliberate.
A published average price for concrete, gravel, or asphalt is wrong for most of the country on any given day, and it goes stale within months. Instead, every calculator that deals with cost has a field for you to enter a quote from your own supplier. The total you get back then reflects your actual market rather than a number somebody typed in two years ago and forgot about.
The same thinking shapes what gets built here. Tools that depend on figures which change every January are kept to a minimum, and where they exist, the page says which year the figures are for.
What This Site Is Not
It is worth being clear about the limits.
I am not a financial adviser, an accountant, an engineer, or a builder. The calculators and guides here explain how something is worked out. They are not advice about what you should do, and they are not a substitute for a professional who can look at your particular situation.
For anything structural, anything with a building code attached, or anything involving a decision about your money, use these tools to understand the problem and then talk to someone qualified.
How the Site Is Funded
Everything here is free to use and there is no paywall, no sign-up, and no premium tier. The site is supported by advertising, which pays for hosting and for the time spent building and checking the tools.
Adverts never affect what a calculator returns, and no tool or guide here is sponsored by a supplier or lender.
Corrections
If you find a figure that looks wrong, I want to know. A calculator that returns a wrong answer is worse than no calculator, and on a site built by one person, readers who check the maths are the best quality control there is.
Get in touch through the contact page and tell me which tool, what you entered, and what you expected. I read everything that comes in.