Put a calculator on your site

Twenty-one free calculators you can embed anywhere: a library resource page, a class site, a client resources page, a blog post. One line of HTML each, and nothing to sign up for.

Pick one

Compare Two StocksTwo stocks or funds on the same dates with the same money: what each became, its worst fall and how long it took to recover. Stock Returns Over TimeWhat an amount in one stock, fund or price file became between two dates: lump sum, dollar-cost averaging and buying the dip side by side. Investment growth calculatorA lump sum, regular contributions, or contributions that step up each year, compounded over time, with an optional inflation adjustment. Compound interest calculatorInterest on interest, at daily, monthly, quarterly or annual compounding. Mortgage calculatorMonthly payment, amount borrowed and total interest. Car loan calculatorMonthly payment and total interest on a vehicle loan. Student loan calculatorMonthly payment, payoff time, and the effect of paying extra each month. Refinance calculatorA current mortgage against a new rate and term, side by side. Mortgage payoff calculatorHow much sooner a mortgage ends with extra monthly payments or a one-off payment, with the interest on each schedule and the extra paid. Down payment calculatorHow long savings take to reach a down payment, or the monthly amount that reaches it within a chosen time, and the loan amount that leaves. CAGR calculatorCompound annual growth rate between a starting and an ending value. Rule of 72 calculatorHow long money takes to double at a given rate, or the rate that doubles it in a given time, with the exact figure alongside the estimate. Inflation calculatorWhat an amount will be worth in today's money after inflation. FIRE calculatorYour FIRE number, the year you reach it as expenses rise with inflation, your savings rate and an optional Coast FIRE number. Withdrawal plannerHow long a balance lasts at monthly, quarterly or yearly withdrawals, or how much you can take out for a set number of years or indefinitely. Savings vs investing calculatorThe same money in a savings account and in investments, with both modeled balances, the difference and today's money. Rent vs buy calculatorBuying a home or renting and investing the difference, from the same money: what each choice leaves you after the years you stay, with the costs of owning, buying and selling. Simple interest calculatorInterest on a principal at a fixed yearly rate, without compounding, and the final amount. Future value calculatorWhat an amount grows to at a fixed rate and compounding frequency, or the starting amount, rate or time needed to reach a target. Present value calculatorWhat a future amount is worth today at a given discount rate and compounding frequency. ROI calculatorThe profit or loss and the return on investment from a starting and an ending value. Profit margin calculatorThe profit and the profit margin from revenue and total costs.

What they have in common

Each fills whatever width you give it, down to phone screens.
They follow your reader's light or dark mode automatically.
They do not track your visitors. No cookies and no analytics. Calculators with a chart also load Chart.js, the open-source chart library, from cdnjs, which sets no cookies.
Free on any site, including commercial ones. The credit line under each widget is optional.

Questions

Email contactus@smartfin.fyi. If you need a calculator that isn't here, say which one and why, since that genuinely shapes what gets built next.