Finance calculators
Pure-math finance tools that don’t require an account, a newsletter signup, or your personal numbers leaving the browser. Tip, tax, and discount calculators ship first; mortgage, compound interest, and salary are next on the runway.
The mortgage calculator returns the monthly payment, total interest paid over the term, and the full amortization schedule from price, down payment, rate, and term — the four inputs that drive the number, with no required email capture. The compound-interest calculator handles arbitrary contribution frequencies (monthly, quarterly, annual) and any compounding period, which matters because the difference between annual and monthly compounding at 7% over 30 years is roughly 10% of the final balance. The salary calculator turns a gross figure into net annual, monthly, weekly, and hourly using the current US federal brackets, FICA, a configurable state rate, and pre-tax 401(k) — surfacing exactly which line item drives each marginal dollar so you can compare two offers in the right column. Tip, sales-tax, and discount calculators handle the everyday cases: split a bill, back-out a pre-tax price, or reverse-engineer the original price from a discount percentage. Every formula is the textbook one; nothing is sent to a server.
Available tools
Salary calculator (US)
Gross → net annual / monthly / weekly / hourly. 2026 federal brackets + FICA + state rate + 401(k) pretax.
Mortgage calculator
Monthly payment + total interest + total paid from price, down, rate, and term.
Compound interest calculator
Future value with periodic contributions and any compounding frequency.
Tip calculator
Tip percent + bill split + optional sales tax.
Sales tax calculator
Add sales tax to a pre-tax price or recover the pre-tax amount from a total.
Discount calculator
Single or stacked discounts — see the effective rate when 20% off meets another 10% off.
Auto loan calculator
Monthly payment, total interest, and amortization schedule from price, down, trade-in, term, APR, sales tax, and fees.
Loan payoff calculator
Months to payoff and interest saved when you add an extra monthly payment. Compares against the no-extra baseline.
Simple interest calculator
Interest and total from principal, rate, and time — the non-compounding I = P × r × t formula.
ROI calculator
Return on investment, net profit, and annualized ROI from your initial and final values.
Inflation calculator
How prices rise and purchasing power erodes at a constant annual rate over time.
Savings goal calculator
The monthly contribution needed to hit a target by a date, with compound growth.
Margin & markup calculator
Profit margin, markup, and the price for a target margin — and why 25% markup is only a 20% margin.
Building society savings calculator
Compare savings, loan, and effective-rate outcomes for a building-society savings plan.
Rotating savings plan calculator
Model contribution order, payout timing, and the effective cost of a rotating savings plan.