Seven free financial calculators that run entirely in your browser. No signup, no email, nothing stored, nothing sent anywhere. Each one shows its assumptions, because a calculator that hides its model is just a number generator.
Debt
Debt Payoff Calculator
Enter your real debts and compare the avalanche method against snowball, and both against paying minimums only. Shows total interest, payoff date, and the order to attack them in — and warns you if a minimum payment barely covers its own interest, which means that debt never clears.
Saving
Emergency Fund Calculator
Sizes your target on how replaceable your income is, not the flat “three to six months” rule — two stable incomes is a different risk from one specialized income. Then it gives you a staged timeline, so the number is a plan instead of a wall.
Savings Goal Calculator
Enter a monthly amount to find out when you reach the goal, or a deadline to find out what it takes per month. Splits contributions from interest so you can see which kind of goal you are actually running.
Budgeting
Monthly Budget Calculator
Checks your actual spending against the 50/30/20 targets and tells you which category is over. It also flags unaccounted money, catches overspending before offering ratio advice, and says plainly when high housing costs are a structural problem rather than a discipline one.
Grocery Budget Calculator
Benchmarks your grocery spend against the USDA Food Plans by household composition — the closest thing the US has to an official answer on what “normal” costs.
Big purchases
Car Affordability Calculator
Works backwards from your income to a sticker price using the 20/4/10 rule, instead of forwards from a monthly payment the dealership picked. Running costs are an input, not an afterthought.
Investing
Compound Interest Calculator
Shows what you contributed, what growth added, and what share of the total is earnings — plus what a fee costs you over the same period, which is usually far more than the percentage suggests.
How we build these
Every calculator here is written from scratch and tested against known-answer cases before it goes live — the debt calculator is verified against the closed-form amortization formula, and the compound interest calculator reproduces the figures quoted in our articles exactly. The numbers you read and the numbers you compute always agree, because they come from the same code.
They are educational tools, not personalized financial advice. Each states its assumptions on the page; where a model simplifies reality, we say so rather than hiding it.