Circle Calculator | EduFun
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Get diameter, circumference, and area for any radius, with formulas for geometry practice.
Key features
- Interactive practice labs for math and language arts that run entirely in the browser.
- Local progress tracking keeps student streaks, accuracy, and preferences private.
- Classroom-ready explanations, hints, and printable summaries support teachers and families.
EduFun tool index
Search engines and caregivers can see every module we offer, from language drills to finance calculators.
- Italian Verb Conjugator. Master every regular Italian verb form with instant grading, hints, and streak analytics.
- Fractions Coach. Simplify, compare, and compute fractions with animated hints and keyboard shortcuts.
- Alfaorder Alphabet Challenge. Drag letters into alphabetical order with multilingual alphabets and timed rounds.
- Pitagoric Table Game. Hide products inside multiplication tables to build confident number fluency.
- GeoGenius Map Challenge. Guess the country from zoomed-in map views with streak tracking and hints.
- BMI Calculator. Estimate body mass index (BMI), healthy weight range, and classification with metric or imperial inputs.
- BMR Calculator. Calculate basal metabolic rate and daily calorie needs using common formulas and activity levels.
- Calorie Intake Planner. Estimate maintenance calories, apply gain/loss goals, and get suggested macros for each day.
- Body Fat %. Estimate body fat using the U.S. Navy method and interpret categories with metric or imperial measurements.
- Pregnancy Due Date. Project an estimated due date, gestational age, and trimester timeline from the last period date.
- Reaction Time Tester. Measure visual reflexes with a quick tap test, using repeatable trials and average timing.
- BSA & Dosage. Calculate body surface area (Mosteller) and practice dose-scaling math using m^2.
- Compound Interest. Project growth of savings with compound interest over time, including contributions and compounding frequency.
- Loan Payment. Estimate monthly payments and amortization schedules, including total interest and payoff timeline.
- Credit Card Payoff. Estimate payoff date, total interest, and time saved when adding extra monthly payment toward credit card debt.
- Debt-to-Income (DTI). Calculate front-end and back-end debt-to-income ratios from housing and recurring debt compared to gross monthly income.
- Emergency Fund Planner. Set a target cushion based on essential monthly expenses and estimate how long it takes to fully fund it.
- Break-Even Calculator. Find break-even units, break-even revenue, and units needed for a target profit from costs and selling price.
- Savings Goal Planner. See how long it takes to reach a target with monthly contributions and optional interest.
- Mortgage Calculator. Estimate principal and interest payments based on price, down payment, term, and rate for quick comparisons.
- Paycheck Calculator. Forecast take-home pay after estimated taxes and deductions, with a clear gross vs net breakdown.
- Tip & Split. Split a bill with customizable tip percentages and per-person totals for percentage and rounding practice.
- Savings Planner. Project future balance with starting cash, contributions, and interest, with an easy timeline summary.
- ROI Calculator. Find net gain and return on investment in dollars and percent for quick side-by-side comparisons.
- Simple Interest. Calculate interest and total amount without compounding, with a simple formula breakdown.
- Markup & Margin. Compare profit margin and markup from cost and price for business-math practice.
- Inflation (Real vs Nominal). Estimate future costs and purchasing power given an inflation rate, comparing real vs nominal values.
- Sales Tax Calculator. Add tax to a pre-tax price or extract tax from a tax-inclusive total with a clear line-item breakdown.
- Discount Calculator. Calculate markdown amount, final price, and effective savings after discount, coupon, and optional sales tax.
- Currency Exchange Calculator. Convert between currencies with a custom exchange rate, including inverse rate and side-by-side totals.
- Percentage Change. Find percentage increase or decrease between two values with clear formula steps.
- GPA Calculator. Convert course grades and credits into a semester GPA on the standard 4.0 scale.
- Final Grade Calculator. Calculate the exam score needed on a weighted final to reach a target overall course grade.
- Fraction Simplifier. Reduce fractions to lowest terms with step-by-step explanation and GCD work shown.
- Quadratic Solver. Solve ax^2 + bx + c with roots, discriminant steps, and real or complex solutions.
- Circle Calculator. Get diameter, circumference, and area for any radius, with formulas for geometry practice.
- Prime Factorization. Decompose integers into primes, count divisors, and label number types with clear factor output.
- GCD, LCM & Ratio. Compute the greatest common divisor, least common multiple, and simplified ratios for lists of integers.
- Permutations & Combinations. Calculate nCr and nPr for counting problems, probability, and statistics practice.
- Triangle Solver. Solve sides, angles, and area for SSS, SAS, ASA, or AAS sets with instant validation and clear results.
- Pythagorean Explorer. Check right triangles and browse classic and primitive triples for quick lesson examples.
- Area & Volume Builder. Compute area/perimeter and volume/surface area across common shapes with quick formulas.
- Descriptive Stats. Find mean, median, mode, range, variance, and spread for any data set, with quick summaries.
- Z-Score & Percentile. Convert raw scores to z-scores and percentile ranks for normal distributions, with interpretation-ready output.
- Binomial Probability. Compute exact and cumulative probabilities for repeated trials, including at-least and at-most results.
- Normal Probability. Find the probability between bounds for any normal distribution, including tail areas and z-scores.
- Dice Probability. Get exact odds for rolling any sum with custom dice and sides, useful for games and probability lessons.
- Spread & Deviation. Compute mean absolute deviation, variance, and standard deviation for quick dataset summaries.
- Linear Regression. Fit a best-fit line, correlation coefficient, and predictions for paired data in labs and projects.
- Unit Converter. Convert common length, mass, and temperature units across classroom-friendly measurement systems.
- Speed, Distance & Time. Solve speed = distance / time with unit conversions and rearranged formulas for quick checks.
- Half-Life Decay. Estimate decay using half-life or decay constant, with remaining quantity over time.
- Ohm's Law. Solve for voltage, current, or resistance from any two known values, with units and formula reminders.
- Fuel Cost Calculator. Estimate trip fuel usage and cost from distance, vehicle efficiency, and fuel price across common unit systems.
- Coordinate Tools. Convert decimal degrees to/from DMS and compute great-circle distance, bearing, and midpoint for maps.
- AI Token Cost. Estimate cost per request plus monthly and annual spend from token usage and per-million pricing.
- Words Per Minute. Run a quick typing test to measure speed and accuracy, with timed passages and repeatable practice.
- Age Calculator. Find exact age, next birthday, and total days lived between two dates, with calendar-friendly results.
- Time Zone Comparator. Compare two time zones and plan shared meeting windows with offsets and suggested schedules.
- Date Duration Calculator. Count total days, weeks, weekdays, and weekend days between two dates with optional inclusive counting.