Every calculation.
One simple place.
Fast, accurate and free online calculators for everyday life, work, finance, health and more.
What you will find here
SmartKitio calculators cover the arithmetic people actually open a browser for: percentages and ratios, loan-style illustrations, body-weight screening numbers, date spans, and everyday money splits. Each calculator shows the formula it uses so you can check the same steps elsewhere.
Math calculators
Percentages (of, reverse, and change), averages, fractions, and ratios. Start here when the question is pure arithmetic.
Finance calculators
Mortgage and loan payment illustrations, compound interest, discounts, profit margin, and ROI. Results are examples from the published formulasânot lender offers.
Health & fitness calculators
BMI, BMR, calorie estimates, and related body-weight tools. These are screening or planning numbers, not medical advice.
Date & time calculators
Age, days between dates, working days, and time-card style totals when you need calendar math without a spreadsheet.
Everyday calculators
Tips, splitting a bill, fuel cost, GPA, and similar daily decisions.
Related guides
Read a longer explanation, then return to a tool when you need a result.
- How to Calculate Percentages
- Percentage Increase vs Percentage Decrease
- How to Calculate Percentage Difference
- How to Calculate BMI
Popular Calculators
Our most frequently used tools.
Percentage
Work out a percentage of a number, the reverse (âX is what percent of Y?â), or how much a value has gone up or down.
Loan
Estimate equal installments on an amortizing loan, plus total interest, from the amount borrowed, annual rate, and length in years.
Mortgage
Estimate the loan payment on a home purchase from price, down payment, rate, and term. Add tax, insurance, and fees if you want a fuller monthly picture.
Compound Interest
See how a balance can grow when interest is added to the principal, with an optional regular deposit.
BMI
Calculate body mass index from height and weight. BMI is a population screening measure, not a verdict on health.
Pregnancy Due Date
Estimate a due date from the first day of the last menstrual period by adding 280 days (40 weeks).
Calories
Estimate daily energy need as BMR times an activity factor, then see a moderate deficit and surplus.
Age
Find age as years, months, and days from a date of birth to today or to another date you choose.
Explore Categories
Find exactly what you need by browsing our organized collections.
All Calculators
Explore our collection of free online calculators.
Age Calculator
Find age as years, months, and days from a date of birth to today or to another date you choose.
BMI Calculator
Calculate body mass index from height and weight. BMI is a population screening measure, not a verdict on health.
Calorie Calculator
Estimate daily energy need as BMR times an activity factor, then see a moderate deficit and surplus.
Compound Interest Calculator
See how a balance can grow when interest is added to the principal, with an optional regular deposit.
Loan Calculator
Estimate equal installments on an amortizing loan, plus total interest, from the amount borrowed, annual rate, and length in years.
Mortgage Calculator
Estimate the loan payment on a home purchase from price, down payment, rate, and term. Add tax, insurance, and fees if you want a fuller monthly picture.
Percentage Calculator
Work out a percentage of a number, the reverse (âX is what percent of Y?â), or how much a value has gone up or down.
Pregnancy Due Date Calculator
Estimate a due date from the first day of the last menstrual period by adding 280 days (40 weeks).
Salary Calculator
Convert a wage between hourly, monthly, and yearly using the working hours you specifyânot a fixed 2,080-hour assumption unless you choose it.
Time Card Calculator
Turn clock-in and clock-out times into hours and minutes for a simple time card.
Tip Calculator
Work out a tip from the bill and a percentage, then optionally divide the total among the people paying.
Average Calculator
Paste a list of numbers to see the arithmetic mean, the median, the sum, how many values you entered, and the range.
BMR Calculator
Estimate calories burned at rest from age, sex, height, and weight. This page uses the Mifflin-St Jeor equation.
Date Difference Calculator
Count how many days separate two dates, using real calendar dates so month lengths and leap days are included.
Discount Calculator
Turn a percent off into a sale price, or work backwards from the original and sale prices to the discount rate.
Fraction Calculator
Add, subtract, multiply, or divide two fractions, then read the simplified fraction, a mixed number, and a decimal.
Fuel Cost Calculator
Estimate what a trip costs in fuel from distance, how much the vehicle uses, and the price of fuel.
GPA Calculator
Enter each course grade and its credits. The GPA is the credit-weighted average of the grade points.
Ideal Weight Calculator
Compare three height-based ideal-weight formulas and the WHO healthy BMI weight band for the same height.
Ovulation Calculator
Estimate ovulation around 14 days before the next period, from cycle length and the last period start.
Profit Margin Calculator
See profit, margin, and markup from a cost and a selling price. Margin and markup use different denominators.
Ratio Calculator
Simplify a ratio, share a total in that ratio, or fill in a missing term in a proportion.
ROI Calculator
Measure a simple return: profit divided by what you put in.
Split Bill Calculator
Split a total evenly. For tip-plus-split in one step, use the tip calculator.
Working Days Calculator
Count weekdays (MondayâFriday) between two dates. Holidays are not removed unless you adjust the dates yourself.