Money calculators

Each money tool is one decision: a sale price, a tip split, a markup versus a margin, a loan payment, an extra principal payment, a monthly deposit, or what inflation does to a dollar you typed. They do not share a cart or an account. Tax is never assumed. A discount page does not add GST. A mortgage page does not add property tax or default insurance.

Loans use the standard payment formula. The mortgage and auto loan pages give the scheduled principal-and-interest payment and the interest over the full term. The payoff page starts from a balance you already have and shows what an extra monthly amount does to the months and the interest. If the regular payment does not cover interest, it says so instead of inventing a payoff date.

Compound interest grows a balance. With no extra deposit it uses the compounding frequency you pick. With a monthly deposit it adds that deposit and then grows the balance at that same frequency. Simple interest does not roll interest back into the balance. Savings goal solves for the deposit when you already know the date and the dollar target. Inflation is a separate multiplication. A savings rate and an inflation rate do not cancel inside one form.

Markup and margin are different percents of different bases. A 50 percent markup on cost is not a 50 percent margin on price. Break-even turns a price cut into a larger unit count, because the contribution on each sale got smaller. Sales tax is a rate you type. Canadian provincial presets live on the GST/HST page, not here.