CalcPerks

About CalcPerks

CalcPerks is a free collection of online calculators and tools built to give you fast, accurate answers to everyday questions — from mortgage payments and compound interest to your exact age or BMI.

Our mission

We believe useful tools should be free, instant and easy to use. Every calculator works in your browser, needs no sign-up, and never asks for personal data to give you a result.

Who this site is for

We build for the person who needs one good number and needs it now — not for specialists with professional software. In practice that means:

  • someone working out whether a mortgage or car loan is affordable before they walk into a bank;
  • a freelancer checking a margin, a tax figure or an hourly rate between jobs;
  • a person tracking calories, macros or a training pace who wants the arithmetic done properly;
  • anyone counting days to a deadline, converting units, or pricing up paint for a room;
  • students and teachers who want to see the formula alongside the answer rather than a black-box result.

If you are a professional who needs authoritative figures for advice or filing, our tools can help you sanity-check — but your own software and your own judgement should be what you rely on.

How our calculators work

Each tool uses established, transparent formulas — explained on every page so you can understand the result, not just read it. Financial results are estimates for planning purposes and should not be treated as professional advice.

How we build and verify each calculator

A calculator is only worth using if you can tell where its answer came from. Every tool here goes through the same process before it is published:

  • We pick a named, published formula.Not an approximation we invented. The amortized loan payment formula, the Mifflin–St Jeor equation for BMR, the US Navy circumference method for body fat, Naegele's rule for a due date, the standard compound interest formula — each tool is built on a source a reader can look up and check.
  • We state the formula in the page body. The maths is written out in the supporting content, not hidden in the code. That means anyone can audit our result with a pen and paper or a spreadsheet, and can see exactly which assumptions we made.
  • We check the worked examples against the live tool.The example numbers in each page's explanation are not decorative. They are entered into the calculator and confirmed to produce the figure the text claims, so the article and the tool can never quietly drift apart.
  • We cover the edge cases. Zero and negative inputs, leap years, unit switching between metric and imperial, rounding behaviour and very large values are exercised so the tool fails clearly rather than returning nonsense.
  • We re-check when things change. When a rate, a threshold or a convention that a calculator depends on changes, the tool and its explanation are updated together.

Where a formula is genuinely contested — ideal body weight is a good example, with several competing equations still in use — we say so on the page rather than presenting one answer as settled fact.

What we deliberately don't do

  • We don't store your inputs. Calculations run in your browser. Your salary, loan balance, weight or due date is never transmitted to us or saved anywhere.
  • We don't require an account.No sign-up, no email address, no paywall, no “enter your details to see the result”.
  • We don't give personalised advice.We show you the maths; we don't tell you what to do with it. Our tools don't know your credit history, your tax jurisdiction or your medical record, and they never pretend otherwise. See our Disclaimer for the detail, particularly on the finance and health tools.
  • We don't let advertising influence results. The site is ad-supported, but no advertiser has any say over which formula a calculator uses or what number it returns.

Corrections

We get things wrong sometimes, and we would much rather hear about it than not. If a result looks off, an explanation is unclear, or a figure is out of date, tell us through the Contact page. The most useful report includes the calculator name, the exact values you entered, the result you got, and the result you expected with your reasoning.

Here is what we commit to in return: we read every correction, we reply, and where a report is valid we fix the tool, re-verify it against the source formula and update the worked examples and explanation on the page at the same time. If we conclude the tool was right after all, we will tell you why rather than going quiet — and if the confusion came from an unclear explanation, we treat that as our bug and rewrite it.