SmartFin

Works the way SmartFin's FIRE calculator does. The FIRE number today is yearly expenses divided by a withdrawal-rate assumption. Each year savings grow at an assumed return with the yearly savings added, while expenses (and so the FIRE number) rise with inflation; FIRE is the first year savings reach that year's FIRE number, searched up to 60 years. Also gives the savings rate and, with a traditional retirement age, the Coast FIRE number. Use for early retirement / FIRE questions: "how much do I need to retire", "when can I retire", "what's my coast FIRE number". Do not use to test how long an existing balance lasts (use smartfin_calculate_retirement_withdrawal). Returns and inflation are assumptions; excludes taxes.

What a single present amount grows to at a fixed yearly rate with interest added to the balance at a chosen frequency, and the growth over the starting amount (FV = PV x (1 + r/n)^(n x t)). Use for questions about what a lump sum becomes after some years at an assumed rate, or the effect of compounding more often. Do not use for regular contributions (use smartfin_project_savings_growth), for what a real stock did (use smartfin_calculate_investment_return), or for a forecast: one fixed rate is an assumption. To find the starting amount, rate or time instead of the future value, use smartfin_calculate_missing_variable.

What an amount will be worth in today's money after years of inflation at a fixed yearly rate, and what something costing that amount today will cost then. Use for questions about buying power or future prices at an assumed inflation rate. Do not use for historical CPI lookups: this uses one fixed rate, not official index data.

What an amount invested in a US stock or index ETF became over a past period under one strategy: lump_sum (all on the first trading day), monthly (spread on the trading day nearest the 1st of each month) or buy_the_dip (bought after falls of a set % from the latest high), on real daily closing prices (adjusted for splits and reinvested dividends). Returns final value, total and yearly return, worst fall and Sharpe ratio. Use when the user asks about one specific approach, e.g. "what would $5,000 in Microsoft since 2015 be worth" (lump_sum) or "if I'd put money into SPY every month since 2010" (monthly). Do not use to compare strategies (use smartfin_compare_investment_strategies) or for future projections (use smartfin_project_savings_growth). Limits: US-listed S&P 500 companies and major index ETFs only, US dollars, month-level periods.

Monthly payment, total interest and total paid for a fixed-rate loan with monthly payments: mortgage, car, student or personal loan. Give either loan_amount, or home_price with down_payment_pct for a mortgage. Use when the user asks what a loan costs per month or in total, or how the rate or term changes the cost. Do not use for variable-rate loans, interest-only loans, or credit cards. Excludes taxes, insurance and fees.

Finds the one missing number among four that sit in the same equation, a single amount earning one fixed yearly rate with interest added at a chosen frequency (FV = PV x (1 + r/n)^(n x t)): the future value, the starting amount, the annual rate, or the time in years. Use when the user knows three of the four and wants the fourth, e.g. "what rate turns $10,000 into $20,000 in 10 years", "how many years until $10,000 reaches $20,000 at 6%", or "what do I need to start with to reach $50,000". Do not use for regular contributions (use smartfin_project_savings_growth), for what a real investment did (use smartfin_calculate_investment_return), or for a forecast: one fixed rate is an assumption, and a required rate is the arithmetic, not a return to expect. To only grow an amount forward use smartfin_calculate_future_value.

What an amount due in the future is worth today at a fixed yearly discount rate, and the discount between the two (PV = FV / (1 + r/n)^(n x t)). Use for questions about the value today of money received later, at a discount rate the user supplies. Do not use to pick a discount rate (the tool has none of its own), for several payments over time, or for a market price: it discounts one amount at one fixed rate. For growth going forward use smartfin_calculate_future_value.

The profit and the profit margin percentage from revenue and total costs (margin = (revenue - costs) / revenue x 100). A negative margin is a valid result. Use for questions about profit as a share of sales, from two figures for the same period. Do not use for return on money invested (use smartfin_calculate_roi), for taxes, or to say whether a margin is good: the tool reports the figure only. The cost figure is whatever the user supplies, so it says nothing about gross versus net unless they define it.

Works the way SmartFin's withdrawal calculator does, with withdrawals monthly, quarterly or annually and the balance earning a yearly return between them. how_long: how many years a balance lasts at a set withdrawal, optionally rising each year with inflation. how_much: the withdrawal that lasts a given number of years, or that never touches the principal (lasts_forever). Use for "how long will my savings last" or "how much can I withdraw". Do not use to find a savings target (use smartfin_calculate_fire_number). Returns are an assumption; excludes taxes and fees.

The profit or loss and the ROI percentage from an initial investment and a final value (ROI = (final - initial) / initial x 100). Negative results are valid. It is not annualized. Use for questions about the total percentage return on money put in, from two values. Do not use for a return per year (use the CAGR calculator at smartfin.fyi/cagr-calculator.html), for what a real stock returned (use smartfin_calculate_investment_return), or for fees and taxes: include them in the final value yourself.

Compares the modeled balances of a savings account and of an investment after 1 to 50 years, from the same starting amount and the same monthly contribution, the way SmartFin's savings vs investing calculator does. You give the savings rate and the investment return; each is held the same every year. Optional: a yearly increase in the monthly contribution (or one that follows inflation), a yearly fee on investments, and tax on savings interest or investment gains. Returns both modeled balances, money put in, interest, growth, fees and taxes, the difference, the same figures in today's money, the investment return at which both end the same (when a fee or tax is given), and a fixed falling-returns case at −2% a year. Use for questions like "how do 10,000 in savings at 4% and the same amount invested at 7% compare after 20 years" or "how far apart do saving and investing end after 20 years". It reports two modeled balances and does not say which option to choose. Do not use it for historical stock or index returns (use smartfin_compare_investment_strategies) or for account types and their tax rules, which it does not model. Amounts can be in any one currency; none is converted.

The interest earned and the final amount on a principal at a fixed yearly rate over a number of years, when interest is not compounded (interest = principal x rate x time). Use for questions about simple interest on a loan or deposit, such as a short-term note or a bond coupon at a flat rate. Do not use when interest is added back to the balance (use smartfin_calculate_future_value or smartfin_project_savings_growth), for loan payments (use smartfin_calculate_loan_payment), or for taxes and fees: it applies none.

Runs one amount through three ways of buying the same US stock or index ETF over a chosen period, on real daily closing prices (adjusted for splits and reinvested dividends): all at once on the first trading day (lump sum), spread evenly on the trading day nearest the 1st of each month, or bought after the price falls a set % from its latest high. Returns each strategy's final value, total and yearly return, worst fall and Sharpe ratio. Use when the user asks which way of investing would have done better for a specific stock or index over a past period, or what an amount would be worth under each approach. Do not use for one strategy only (use smartfin_calculate_investment_return), for several reference periods at once (use smartfin_compare_time_periods), or for future projections. Limits: US-listed S&P 500 companies and major index ETFs only, prices in US dollars, month-level start and end; results depend on the period and are not a prediction.

Compares buying a home with a fixed-rate mortgage against renting a similar home and investing the money not spent on the home, over the years someone plans to stay, the way SmartFin's rent vs buy calculator does. Both start with the same cash and spend the same each month; whichever costs less that month invests the difference. Returns the modeled money each choice leaves (home sold and loan paid, or kept as equity, against the investments), the difference, the first year-end at which buying leaves at least as much as renting, the starting rent at which both leave the same, the monthly payment, month-one costs and totals. Use when someone asks how renting and buying compare, how long they would need to stay for the two to cross, or what rent matches buying a home. Do not use for rental-property investing, for how much someone can borrow, for tax planning or for adjustable-rate loans. Rates are held constant; income-tax effects of owning and tax on the home sale are not modeled. It reports modeled money only and does not say whether to rent or buy. Amounts can be in any one currency; none is converted.

What a fixed amount in a US stock or index ETF became across reference periods ending today (or on as_of_date): since 2000, since the dot-com peak (24 Mar 2000), since the dot-com crash low (9 Oct 2002), since the 2007 peak (9 Oct 2007), since the 2008 crash low (9 Mar 2009), since 2010, since the COVID low (23 Mar 2020), since the 2022 low (12 Oct 2022), and the last 10, 5 and 1 years. Each row gives lump sum and monthly investing results on daily closing prices adjusted for splits and reinvested dividends. Event dates are S&P 500 closing highs and lows. Use when the user asks how a stock did over several time frames, or names one of these moments ("from the COVID low", "since 2000"). Do not use for a custom start month (use smartfin_compare_investment_strategies). Limits: periods that start before the ticker's price history are skipped and listed with the reason; US dollars; not a prediction.

The HTML to put one of SmartFin's free calculators on a website the user runs: a blog post, a class or library page, a client resources page. One iframe line, free, no sign-up, no cookies or tracking; the widget fills the width it's given and follows the reader's light or dark mode. Calculators: investment (Investment growth calculator), compound_interest (Compound interest calculator), mortgage (Mortgage calculator), car_loan (Car loan calculator), student_loan (Student loan calculator), refinance (Refinance calculator), cagr (CAGR calculator), rule_of_72 (Rule of 72 calculator), inflation (Inflation calculator), fire (FIRE calculator), withdrawal (Withdrawal planner), savings_vs_investing (Savings vs investing calculator), rent_vs_buy (Rent vs buy calculator), simple_interest (Simple interest calculator), future_value (Future value calculator), present_value (Present value calculator), roi (ROI calculator), profit_margin (Profit margin calculator). Use when the user wants a calculator on their own site or asks how to add one. Do not use to calculate anything (use the other smartfin_ tools).

Future balance of savings or an investment growing at a fixed yearly rate, with optional monthly contributions and a chosen compounding frequency. Returns the balance, total paid in and interest earned. Use for forward-looking "how much will I have" questions at an assumed rate. Do not use for what a real stock did in the past (use smartfin_calculate_investment_return). A fixed rate is an assumption, not a forecast.