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Free forever.
A growing collection of calculators and tools — built for speed, designed for clarity, free to use.
10 tools available
I built CalcJar because I kept opening spreadsheets to answer questions that should take five seconds. Every tool here is something I actually use — from estimating take-home pay when comparing job offers, to splitting bills, to finally understanding how compound interest works in practice. No ads (yet), no signup, no nonsense. Just the answer.
More about the site →Most Used Tools
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Paycheck Calculator
Estimate your take-home pay after federal and state tax withholding for all 50 US states.
Finance 📈
Compound Interest Calculator
See how your savings or investments grow over time with compound interest. Includes monthly contribution support.
Finance ⚖️
BMI Calculator
Calculate your Body Mass Index using height and weight. Supports both metric and imperial units with health range indicators.
Health 🧾
Tip Calculator
Calculate tips and split bills between any number of people. Supports custom tip percentages and per-person breakdowns.
Finance 💯
Percentage Calculator
Calculate percentages instantly — find X% of Y, what percent X is of Y, and percentage change between two numbers.
Math All Tools
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Percentage Calculator
Calculate percentages instantly — find X% of Y, what percent X is of Y, and percentage change between two numbers.
Math 🧾
Tip Calculator
Calculate tips and split bills between any number of people. Supports custom tip percentages and per-person breakdowns.
Finance 📈
Compound Interest Calculator
See how your savings or investments grow over time with compound interest. Includes monthly contribution support.
Finance 🎂
Age Calculator
Calculate your exact age in years, months, and days from your date of birth. Also shows days until your next birthday.
Date & Time ⚖️
BMI Calculator
Calculate your Body Mass Index using height and weight. Supports both metric and imperial units with health range indicators.
Health 💰
Paycheck Calculator
Estimate your take-home pay after federal and state tax withholding for all 50 US states.
Finance 🏠
Mortgage Affordability Calculator
Find out how much house you can afford based on income, debts, down payment, and interest rate using the 28/36 rule.
Finance 📊
Markup & Margin Calculator
Instantly convert between markup and margin percentages. Calculate selling price, profit, and cost from any starting point.
Business 🔥
TDEE & Calorie Needs Calculator
Calculate your Total Daily Energy Expenditure and daily calorie targets for weight loss, maintenance, or muscle gain.
Health 🌍
Time Zone Converter
Convert times between any world time zones instantly with DST-aware accuracy and a live world clock.
Date & Time