Calculators

Every formula tested before any interface existed

A calculator that looks right and computes wrong is worse than no calculator, because you will believe it. So each formula here was written and checked against known values before a single pixel of interface was built.

Some of the checks: a $200,000 loan at 6% over 30 years gives $1,199.10 a month. A credit-weighted GPA of A, B+ and C across 3, 4 and 3 credits gives 3.12. 28 February to 1 March is two days in 2024 and one day in 2025. $80 to $100 is a 25% markup and a 20% margin.

They are reproducible on purpose. Check any of them yourself.

Where a calculator should refuse to answer

Several of these divide by one of your inputs, and dividing by zero is undefined. When that happens you get told, rather than shown a confident number that means nothing.

Same principle behind the margin ceiling: a target margin of 100% is arithmetically impossible, so it is flagged instead of producing a price. A tool that always prints something looks more capable and is less useful.

Estimates, and what they are not

The loan calculator is a planning estimate, not a loan offer and not financial advice. The BMI calculator is a general screening number, not a diagnosis and not medical advice, and it deliberately has no weight-goal or calorie features.

Those lines are on the pages themselves rather than buried in a footer, because the moment a number looks authoritative is exactly when its limits need saying.