Free online calculators for money, health, math and everyday decisions
141 calculators in 8 categories, plus a portfolio optimizer and factor analysis for investors. Free to use, with no account.
Calculators by category
A few calculators from each category are listed here. Every category opens in the directory, which has all 141.
Finance calculators
All 69 finance calculatorsBuying or refinancing a home?
The mortgage and real estate guide sorts the calculators by task, from affordability to payoff.
Mortgage and real estate calculatorsInvesting & Trading
Returns, portfolio risk, position sizing and trading breakevens.
- ROI Calculator
- IRR Calculator
- Dividend Yield & Income Growth Calculator
- VaR & CVaR Calculator
- Safe Position Size Calculator
Fitness & Health
Body measures, calories, pregnancy dates and training numbers.
- BMI Calculator for Adults
- Calorie and TDEE Calculator
- Body Fat Calculator
- Pregnancy Due Date Calculator
- Pace Calculator
Math & Statistics
Percentages, averages, notation, division and probability.
- Percentage Calculator
- Average Calculator
- Scientific Notation Calculator
- Long Division Calculator
- Normal Distribution Calculator
Work & Time
Ages, dates, hours worked, salary conversions and overtime.
- Age Calculator
- Date Calculator
- Hours Between Times Calculator
- Hourly to Salary Calculator
- Overtime Calculator
Home & Construction
Areas and material quantities for building and decorating.
All 5 home & construction calculatorsPortfolio optimizer and factor analysis
QuantStock started as a portfolio optimizer, and those tools are still here. They work on price history for the stocks you choose, so they take a little longer than a calculator and answer a different kind of question: how the holdings behave together.
Guides and worked examples
Articles that take one question and work it through with numbers, using the calculators on this site.
- HousingRent vs Buy: Why the Break-Even Year Can ChangeHow selling costs, maintenance, rent growth and invested savings move the year in which buying comes out ahead.
- SavingsHow Much Interest Does $10,000 Earn in a CD?Worked examples at several APYs and terms, and what an early withdrawal costs.
- Portfolio managementPortfolio Rebalancing Calculator: How Much to Buy, Sell and WhenMeasuring drift, a worked 60/40 example, and how to choose a rebalancing threshold.
- Portfolio theoryUnderstanding the Efficient Frontier in Modern Portfolio TheoryWhat the frontier shows and how it helps weigh expected return against risk when choosing an allocation.
How QuantStock calculators work
QuantStock is a free collection of online calculators. It began as a set of tools for investors and now covers everyday questions as well: what a loan will cost, how much to save for retirement, how many calories you use in a day, what grade you need on a final exam, how much paint to buy for a room.
What a calculator page gives you
Most calculator pages open with a filled-in example, so you can see what a result looks like before you type anything. Below the tool, they explain the formula, work through an example with real numbers and say where the estimate stops being reliable. Pages with a schedule, such as a mortgage or loan amortization table, let you download it as a CSV file.
Where the numbers come from
The formulas are standard ones and are named on the page. Where a calculator depends on published figures, it says which: the inflation calculator uses official US CPI data from 1913 onward, the required minimum distribution calculator uses the IRS Uniform Lifetime Table, and the BMI calculator uses the CDC categories for adults.
Your inputs stay in your browser
Calculators run in your browser. The numbers you type are not sent to our servers and are not included in our analytics. The portfolio optimizer and factor analysis are different: they send the tickers and settings you choose to our server, because that is where the price history is kept.
What the results are not
Results are estimates for planning and learning. They are not financial, tax, medical or legal advice, and they cannot take your full situation into account. For a decision that matters, check the result with a qualified professional, and read the disclaimer.
Questions about QuantStock
- Are the calculators free?
- Yes. Every calculator, the portfolio optimizer and factor analysis are free, and none of them needs an account.
- How do I find a calculator?
- Type a word into the search field at the top of this page, such as mortgage, BMI or GPA, or pick a category. The calculator directory lists all 141.
- How accurate are the results?
- The arithmetic follows the formula shown on each page, and newer calculators are tested against independently computed reference values before release. A result is still only as good as its inputs and assumptions, such as an interest rate that never changes or a typical activity level.
- Which countries do the calculators cover?
- Most work anywhere: loans, interest, percentages, dates, health formulas and construction quantities are the same in every country, and many pages accept both metric and US units. The income tax, paycheck, retirement account and Social Security calculators follow United States rules.
- How are the portfolio tools different from a calculator?
- A calculator answers one question from the numbers you enter. The portfolio optimizer and factor analysis work on price history for the stocks you choose, so they can estimate risk, correlation and factor exposure that you could not type in by hand.
- Can I suggest a calculator or report an error?
- Yes. Write to us through the contact page. Error reports are the most useful messages we get.
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