# CalcKits > Smart Calculators for a Better You ## Posts - [How Much to Tip: A Practical Guide](https://calckits.online/how-much-to-tip/): At a sit-down restaurant in the US, 15% to 20% of the pre-tax bill is the usual range, with 20% the common default for good service. - [Compound Interest Formula, Explained with Examples](https://calckits.online/compound-interest-formula/): Compound interest is interest earned on your interest. - [How to Calculate Percentage, Step by Step](https://calckits.online/how-to-calculate-percentage/): Take any number, divide it by 100, and you have one percent of it. Everything else below builds on that single move. ## Pages - [Cooking Converter — Cups, Tablespoons, ml, and Grams](https://calckits.online/cooking-converter/): The recipe says 2 cups of flour. Your jug reads ml. Your scale reads grams. - [Speed Calculator — How Fast Were You Going?](https://calckits.online/speed-calculator/): How fast was I actually going? Distance divided by time. - [Time Duration Calculator — Hours Between Two Times](https://calckits.online/time-duration-calculator/): A shift that starts at 9:47 and ends at 4:23 is not 6.76 hours, and it is not 7 hours either. - [Date Calculator — Add or Subtract Days From Any Date](https://calckits.online/date-calculator/): Deadlines have a habit of landing on Saturdays. Type in a start date and a number of days and this page tells you where you land, weekday included. - [Days Between Dates Calculator — Count the Days](https://calckits.online/days-between-dates-calculator/): Two dates. One number. This page counts the days between them, and tells you the weeks and weekdays too. - [Fuel Cost Calculator — What Will Gas Cost for Your Trip?](https://calckits.online/fuel-cost-calculator/): You know the distance and roughly what your car drinks. The missing piece is what the trip costs, and what each passenger owes. - [Tip Calculator — Split the Bill and Tip Right](https://calckits.online/tip-calculator/): Three friends, one bill, and the quiet standoff over who does the maths. This page ends it in about ten seconds. - [Age Calculator — How Old Am I Today?](https://calckits.online/age-calculator/): Put in a date of birth and you get your age in years, months, and days, plus the total days you have lived and the wait until your next birthday. - [Area Calculator](https://calckits.online/area-calculator/): You are standing in a room, wondering how much flooring it needs. The room is 12 metres long and 8 wide. Multiply them: 96 square metres. - [Unit Converter](https://calckits.online/unit-converter/): A recipe from an American site, a road sign in miles, a weather forecast in Fahrenheit. Three different unit systems, one small piece of arithmetic each. - [GPA Calculator](https://calckits.online/gpa-calculator/): Four courses, one number that follows you onto every application. An A, a B, an A, and a B across 13 credits come out at 3.46. - [Ratio Calculator](https://calckits.online/ratio-calculator/): 18:24 looks clumsy. 3:4 says the same thing, with smaller numbers. - [Average Calculator](https://calckits.online/average-calculator/): Your class scored 2, 4, 4, 6 on a quiz. What was the average? - [Fraction Calculator](https://calckits.online/fraction-calculator/): Half a cup of flour, a third of a cup of sugar. How much dry stuff is that in total? You can't just add the tops. - [Percentage Calculator](https://calckits.online/percentage-calculator/): The jacket is $80, the tag says 25% off, and you want the real price before you reach the till. You save $20. You pay $60. - [BMR Calculator](https://calckits.online/bmr-calculator/): Lie still for a day, eat nothing, move nothing, and your body would still burn energy. Breathing. Keeping your heart beating. Holding your temperature. - [Ideal Weight Calculator](https://calckits.online/ideal-weight-calculator/): There is no single weight that is right for everyone at your height. - [Pregnancy Due Date Calculator](https://calckits.online/pregnancy-due-date-calculator/): The first question after a positive test is usually: when? This calculator gives you a date to plan around. It is a planning date, not a promise. - [Water Intake Calculator](https://calckits.online/water-intake-calculator/): Eight glasses. A gallon. Half your body weight in ounces. - [Body Fat Percentage Calculator](https://calckits.online/body-fat-calculator/): The scale tells you one thing. It cannot tell you what that weight is made of. - [Calorie Calculator](https://calckits.online/calorie-calculator/): Eat near your maintenance number and your weight tends to stay put. Eat a few hundred less each day and it tends to drift down. - [BMI Calculator](https://calckits.online/bmi-calculator/): A doctor's office, a gym induction, an insurance form. BMI turns up in all three, and most people meet it without anyone explaining what it is. - [Sales Tax Calculator](https://calckits.online/sales-tax-calculator/): A $100 purchase at 8.25% carries $8.25 in tax. The total is $108.25, $8.25 more than the sticker price. Budget to the sticker and you come up short. - [Discount Calculator](https://calckits.online/discount-calculator/): Sale tags are built to make you feel like you are getting a deal, not to make the math easy. "25% off" on an $80 jacket is simple enough. - [Savings Goal Calculator](https://calckits.online/savings-goal-calculator/): “Save $20,000” is a wish. “Put aside $523.81 a month for three years” is a plan. - [Simple Interest Calculator](https://calckits.online/simple-interest-calculator/): Year three earns the same interest as year one: $250. That flat line is the signature of simple interest. - [Retirement Calculator](https://calckits.online/retirement-calculator/): An extra $88 a month is the difference between $874,826.18 and $1,000,000. - [Loan Calculator](https://calckits.online/loan-calculator/): A low monthly payment can hide a long term and a lot of interest. - [Compound Interest Calculator](https://calckits.online/compound-interest-calculator/): What does $200 a month actually become? - [Mortgage Calculator](https://calckits.online/mortgage-calculator/): The number your lender quotes is never the whole number. - [Frequently Asked Questions](https://calckits.online/faqs/): Quick answers to the questions we get most often. If you do not find your answer here, please contact us. - [Cookie Policy](https://calckits.online/cookie-policy/): This page explains what cookies are, which ones CalcKits uses, why, and how you can manage them. For data overall, see our Privacy Policy. - [Disclaimer](https://calckits.online/disclaimer/): CalcKits provides calculators and guides for general information only. Please read this page before relying on any result. - [Terms of Use](https://calckits.online/terms/): These terms cover use of CalcKits (calckits.online). By using the site you agree to them. If you do not agree, please do not use the site. - [Contact Us](https://calckits.online/contact/): Send us a message with the form below. We read every message, and we aim to reply within 2 business days. - [About CalcKits](https://calckits.online/about/): CalcKits is a small site with a simple job: help you work out a number and understand what it means. - [Blog](https://calckits.online/blog/) - [Everyday Calculators](https://calckits.online/calculators/everyday/): Eight tools for the small sums that come up in daily life: how old you are, what the bill splits to, what the trip costs, how long until the deadline. - [Math Calculators](https://calckits.online/calculators/math/): Seven tools for the arithmetic that shows up in real life: percentages at the shops, averages in a gradebook, ratios in a recipe, conversions in a workshop. - [Health Calculators](https://calckits.online/calculators/health/): Seven quick checks for the body numbers people actually use: weight, calories, water, and the rest. - [Finance Calculators](https://calckits.online/calculators/finance/): Money decisions get easier when you can see the numbers. - [All Calculators](https://calckits.online/calculators/): Every CalcKits calculator in one place — free, no sign-up, and each one shows the working behind the answer. Pick a category below, or jump straight to a tool. - [Home](https://calckits.online/): Free calculators for money, health, maths, and everyday life. No sign-up. No clutter. Just the answer, with the working shown. - [Privacy Policy](https://calckits.online/privacy-policy/): This policy explains what data CalcKits collects, why, and the choices you have. [comment]: # (Generated by Hostinger Tools Plugin)