Fast, accurate, and free online calculators for finance, health, and work โ built to run entirely in your browser.
Enter what you put in and what you got back, and this tool instantly works out your net profit and ROI percentage โ useful for judging a stock position, a marketing campaign, a rental property, or any purchase you're weighing against its payoff.
What is Return on Investment (ROI)? ROI is a popular financial metric used to evaluate the efficiency or profitability of an investment relative to its initial cost.
How is ROI calculated? ROI is calculated by subtracting the initial cost of the investment from the final value (net profit), dividing that number by the initial cost, and multiplying by 100 to get a percentage.
What is considered a good ROI? Generally, an annual ROI of 7% to 10% or higher is considered strong for stock market investments, while business or marketing ROI targets are often much higher (e.g., 500% or 5:1 ratio).
Can ROI be negative? Yes. A negative ROI simply means the amount returned was less than the amount originally invested, so the investment lost money overall rather than generating a profit.
Should I use ROI on its own to make a decision? ROI is a helpful starting point, but it ignores risk, time horizon, and taxes โ pairing it with those factors (and, for deeper dives, our compound interest calculator) gives a fuller picture.
Plug in the home price, down payment, interest rate, and loan term to see your estimated monthly payment, total interest, and overall loan cost before you talk to a lender.
What is PITI in a mortgage? PITI stands for Principal, Interest, Taxes, and Insuranceโthe four main components of a monthly mortgage payment.
How does down payment affect my monthly cost? A larger down payment reduces the principal loan balance, which directly lowers monthly interest and removes the need for Private Mortgage Insurance (PMI) if you reach 20% down.
Does a longer loan term always cost more overall? Usually yes โ stretching a loan from 15 to 30 years lowers the monthly payment but generally increases the total interest paid over the life of the loan, since you're borrowing the money for longer.
Why does the interest rate matter so much? Even a difference of half a percentage point can change your monthly payment noticeably and add up to tens of thousands of dollars in extra interest over a 30-year term.
Body Mass Index gives a quick, widely used snapshot of whether your weight falls in a typical range for your height. It's a screening tool, not a diagnosis โ enter your numbers below to see where you land.
What do the BMI categories mean? Under 18.5 is generally classed as underweight, 18.5โ24.9 as normal weight, 25โ29.9 as overweight, and 30 and above as obesity, according to the standard World Health Organization ranges.
Is BMI accurate for everyone? BMI is a useful population-level screening tool, but it doesn't account for muscle mass, bone density, age, or sex, so it can be less accurate for athletes, older adults, and pregnant women.
Should I make health decisions based on BMI alone? No โ BMI is best used as a starting conversation point. Waist circumference, body composition, and a conversation with a healthcare provider give a much fuller picture of health.
Work backwards from the income you actually want to take home to the hourly rate you need to charge, once realistic business expenses and billable hours are factored in.
How many billable hours can a freelancer actually work per week? Most full-time freelancers work 20 to 25 billable hours per week, with remaining hours spent on admin, client acquisition, and accounting.
What expenses should freelancers include in their calculations? Account for self-employment taxes, health insurance, software subscriptions, hardware upgrades, accountant fees, and unpaid vacation days.
Should I charge hourly or fixed project rates? While an hourly calculator helps set your minimum wage floor, charging fixed or value-based project rates is often more lucrative as you gain efficiency.
How often should I revisit my rate? Many freelancers reassess pricing at least once a year, or whenever their skills, demand, or cost of living shifts meaningfully.
A quick way to translate a gross annual income and an estimated effective tax rate into an approximate take-home figure, broken down by year and by month.
What is the difference between marginal and effective tax rate? Your marginal rate is the tax percentage applied to your last dollar of income. Your effective rate is the actual overall percentage of total income paid after deductions.
How can I lower my taxable income? Contributing pre-tax dollars to retirement accounts (401k, IRA), Health Savings Accounts (HSAs), and claiming legal business deductions lower your taxable total.
What is net take-home pay? Take-home pay is your gross salary minus all federal, state, and payroll taxes, along with voluntary deductions like health insurance premiums.
Does this tool replace a real tax return? No โ it's meant for quick, rough planning only. Actual tax owed depends on your filing status, deductions, credits, and local rules, so a tax professional or official calculator should be used for filing.
See how a lump-sum principal plus optional monthly contributions can grow over time as interest compounds on itself. A deeper walkthrough of the math lives on our dedicated compound interest guide.
How does compound interest work? Compound interest is interest earned on both your initial principal investment and on the accumulated interest from previous periods ("interest on interest").
What is the Rule of 72? The Rule of 72 is a quick shortcut to estimate how many years it will take to double your investment: divide 72 by your annual interest rate (e.g., 72 / 8% = 9 years).
What is a reasonable compound annual growth rate to assume? Historically, the broad stock market (S&P 500) has averaged an annual return of around 7% to 10% before inflation adjustments.
Does this calculator account for taxes or fees? No โ it shows gross growth only. Taxes, account fees, and inflation will all reduce the real, spendable value of the final balance shown here.
Handles the three percentage questions people run into most: finding a part of a whole, finding what percent one number is of another, and finding the percentage change between two values.
How do you calculate percentage change? Subtract the old value from the new value, divide the result by the absolute old value, and multiply by 100.
How do you calculate percentage increase? If a value goes from X to Y, the percentage increase is ((Y - X) / X) ร 100.
What is the easiest way to find 10% of a number? Simply move the decimal point one position to the left (e.g., 10% of 250 is 25).
Why do percentage calculations trip people up? Mostly because it's easy to mix up which number is the "whole" and which is the "part," especially in percentage-change problems where the direction of the comparison matters.
Estimates your Basal Metabolic Rate and Total Daily Energy Expenditure using the widely referenced Mifflin-St Jeor equation, then suggests calorie targets for weight loss or muscle gain.
What is TDEE? Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns per day, including base metabolism and daily activity.
What is BMR? Basal Metabolic Rate (BMR) is the amount of energy your body burns at complete rest just to keep vital organs functioning.
How many calories should I eat to lose weight? Eating a deficit of 500 calories below your maintenance TDEE typically results in about 0.5 kg (1 lb) of fat loss per week.
Is the Mifflin-St Jeor equation the most accurate option? It's one of the most widely trusted formulas for estimating BMR in the general population, though individual metabolism can still vary from the estimate for reasons like muscle mass and genetics.
Welcome to our comprehensive suite of online calculators designed to streamline your financial planning, career trajectory, and health goals. Whether you are estimating monthly mortgage payments, calculating business ROI, setting hourly freelance rates, projecting compound savings, or tracking health metrics through BMI and calorie intake, our browser-based tools offer instant calculations with no data collection.
We built this page around a single idea: the math behind everyday financial and health decisions shouldn't require a spreadsheet, an account, or a download. Every calculator on this page runs directly in your browser tab, recalculates instantly as you adjust the inputs, and never sends your numbers anywhere else.
Most visitors land here with a specific, real-world question in mind โ "can I afford this house," "is this investment worth it," "what should I charge as a freelancer," or "how many calories should I actually be eating." Rather than digging through several different single-purpose sites, this suite keeps the eight tools people ask for most often in one convenient, tabbed interface.
ROI, mortgage, compound interest, and tax tools help you compare options before you commit real dollars.
The freelance rate calculator turns a target income into a concrete number you can put on an invoice.
The percentage calculator handles the quick "what percent is that" questions that come up constantly.
BMI and TDEE give a fast, free starting point for weight and nutrition planning.
Each calculator uses standard, widely published formulas โ the classic ROI formula, the amortizing-loan payment formula for mortgages, the Mifflin-St Jeor equation for calorie needs, and the compound interest formula for savings growth. That means the arithmetic itself is solid, but every output is still an estimate: real mortgages include fees and taxes, real investments carry risk and volatility, and real metabolism varies from person to person. Treat every result here as a well-informed starting point for a conversation with a lender, advisor, or clinician, not a final answer.
None of the calculators on this page store, transmit, or log the numbers you type in. Every calculation happens locally in JavaScript running inside your own browser tab, and closing or refreshing the page clears everything instantly. You can find the full details in our Privacy Policy.
Want a deeper dive into the math behind two of the most popular tools? Read the full ROI Calculator guide or the full Compound Interest Calculator guide for formulas, worked examples, and extended FAQs.
Each tool above also has its own dedicated guide page with the full formula, a worked example, and answers to the questions people ask most.
Profit & return on investment
Monthly payments & interest
Healthy weight range check
Find your target hourly rate
Estimated take-home pay
Savings growth over time
Quick percentage math
Daily energy needs