Free online calculators.
Instant answers, formulas included.

195 fast, mobile-friendly calculators for money, health and everyday math — each with the exact formula, a worked example and answers to common questions. No sign-up, no downloads.

Finance

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Compound Interest CalculatorSee how your money grows with monthly, quarterly or yearly compounding. Loan EMI CalculatorMonthly EMI, total interest and total payment for any loan. Mortgage CalculatorMonthly payment and lifetime interest for a home purchase. SIP CalculatorMaturity value of a monthly mutual fund SIP. Simple Interest CalculatorQuick interest on a principal using SI = P×R×T. FD CalculatorMaturity value of a bank fixed deposit. Salary CalculatorConvert between hourly, monthly and annual pay. Income Tax Calculator (India)India tax for FY 2025-26 under the new regime, with rebate. GST CalculatorAdd GST to a price or extract it from a total. Currency ConverterLive exchange rates for 30+ major currencies. PPF Calculator15-year PPF maturity value with tax-free interest. RD CalculatorMaturity value of a monthly recurring deposit. Inflation CalculatorWhat today's money will be worth in the future. ROI CalculatorTotal ROI and annualized return (CAGR) on any investment. Profit Margin CalculatorProfit, margin % and markup % from cost and price. Break-Even CalculatorUnits and revenue needed to cover your costs. Credit Card Payoff CalculatorHow long until your card is paid off — and what it costs. Auto Loan CalculatorMonthly car payment and the vehicle's true financed cost. Savings Goal CalculatorThe exact monthly saving that reaches your target. Gratuity CalculatorGratuity payable under India's 15/26 formula.

Health & Fitness

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BMI CalculatorBody mass index and healthy weight range in seconds. Calorie CalculatorDaily calories to maintain, lose or gain weight. Age CalculatorExact age in years, months and days from your birth date. Pregnancy Due Date CalculatorEstimated due date and current week of pregnancy. BMR CalculatorCalories your body burns at complete rest. Body Fat CalculatorBody fat percentage from tape measurements (US Navy method). TDEE CalculatorTotal calories you burn per day, at every activity level. Ideal Weight CalculatorIdeal weight for your height by multiple formulas. Water Intake CalculatorDaily water target in liters, cups and glasses. Macro CalculatorDaily protein, carbs and fat targets in grams. Protein Intake CalculatorDaily protein target in grams, by body weight and goal. Heart Rate Zone CalculatorYour 5 training zones — fat burn to VO2 max. Body Surface Area CalculatorBSA in m² — Mosteller and Du Bois formulas. Lean Body Mass CalculatorFat-free mass via the Boer formula or your body fat %. Waist-to-Hip Ratio CalculatorWHR with WHO risk categories — what BMI misses. Calories Burned CalculatorCalories burned by activity, weight and duration. Steps to Calories CalculatorSteps → distance and calories, from your height & weight. Ovulation CalculatorOvulation day, fertile window and next period. Running Pace CalculatorPace per km & mile from distance and time, with splits. One Rep Max Calculator1RM from any set, plus your %1RM training table. Smoking Cost CalculatorYour cigarette spend per year — and its invested value. Blood Pressure CheckerWhere your BP reading falls — normal to hypertensive.

Math & Everyday

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Percentage CalculatorX% of Y, X as a % of Y, and % change — all in one. Discount CalculatorFinal price after a discount — and what you actually save. Tip CalculatorTip amount, total and per-person split for any bill. Date Difference CalculatorExact days, weeks and months between any two dates. Percentage Change CalculatorPercentage increase or decrease between two numbers. Fraction CalculatorAdd, subtract, multiply or divide fractions — simplified. GCD & LCM CalculatorGCD (HCF) and LCM of two or more numbers at once. Square Root CalculatorSquare root and cube root of any number. Exponent CalculatorAny base to any power — negatives and fractions included. Quadratic Equation SolverSolve ax² + bx + c = 0 — roots, discriminant, vertex. Mean, Median & Mode CalculatorAverage, median, mode and range of any number list. Standard Deviation CalculatorSample & population SD, variance and mean from a list. Probability CalculatorProbability, percentage and odds from outcomes. Permutation & Combination CalculatornPr and nCr — arrangements and selections, computed exactly. Number Base ConverterBinary ↔ decimal ↔ hex ↔ octal in one tool.

Unit Converters

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Length ConverterMeters, feet, inches, miles, km and more — all at once. Weight ConverterKg, lbs, grams, ounces and stones — all at once. Temperature ConverterCelsius ↔ Fahrenheit ↔ Kelvin with formulas. Area ConverterSq ft, sq m, acres and hectares — all at once. Volume ConverterLiters, gallons, cups, mL and fl oz — all at once. Speed ConverterKm/h, mph, m/s and knots — all at once. Time ConverterSeconds to years — any duration in every unit. Data Storage ConverterBits, bytes, KB, MB, GB, TB — all at once. Cm to Inches ConverterCm ↔ inches, with height shown as feet + inches. Kg to Lbs ConverterKg ↔ lbs (with stones), using the exact factor. Miles to Km ConverterMiles ↔ km with the exact factor and pace references. Liters to Gallons ConverterLiters ↔ US & UK gallons, side by side. Pressure ConverterBar, psi, kPa, atm and mmHg — all at once. Energy ConverterJoules, calories, kWh and BTU — all at once. Power ConverterWatts, kW, hp and PS — all at once.

Date & Time

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Working Days CalculatorBusiness days between two dates, minus weekends and holidays. Days Until CalculatorCountdown to any date in days, weeks and months. Work Hours CalculatorClock-in to clock-out, minus breaks — in hh:mm and decimal. Time Zone ConverterConvert meeting times across world time zones, DST included. Week Number CalculatorISO week number for any date. Day of the Week CalculatorWhat weekday any date falls on — past or future. Date Add & Subtract CalculatorAny date ± days, weeks, months or years. Sleep CalculatorIdeal bedtimes and wake times based on 90-minute cycles. Time to Decimal CalculatorHH:MM ↔ decimal hours, both directions. Unix Timestamp ConverterEpoch seconds ↔ human dates, local and UTC. Leap Year CalculatorCheck any year, with the century-rule explained. Military Time Converter24-hour ↔ AM/PM, with midnight and noon done right. Add & Subtract Time CalculatorClock time ± hours and minutes, across midnight.

Education

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GPA CalculatorSemester GPA from letter grades and credit hours. CGPA CalculatorCumulative CGPA from your semester GPAs and credits. CGPA to Percentage CalculatorCGPA ↔ percentage with the ×9.5 rule or a custom factor. Grade CalculatorOverall course grade from weighted scores. Final Grade CalculatorThe exact score you need on the final exam. Exam Marks Percentage CalculatorMarks obtained ÷ total → percentage and grade. Attendance CalculatorYour attendance % — and the path back to 75%. Percentile CalculatorPercentile rank of a score within a dataset. Reading Time CalculatorHow long any text or book takes to read. Speech Time CalculatorWords ↔ minutes for speeches and presentations. Word CounterWords, characters, sentences — paste and count.

Business & Marketing

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ROAS CalculatorReturn on ad spend — and the break-even ROAS you need. CTR CalculatorClick-through rate from clicks and impressions. CPC CalculatorCost per click, and the max CPC you can afford. CPM CalculatorCost per 1,000 impressions — solve any of the three. Conversion Rate CalculatorYour CR — and the value of each extra point. Customer Lifetime Value CalculatorCLV from order value, frequency and lifespan — plus LTV:CAC. Churn Rate CalculatorChurn %, retention, and implied customer lifetime. MRR & ARR CalculatorMRR, ARR, and the 12-month compounding projection. Burn Rate & Runway CalculatorNet burn and months of runway from cash and costs. NPS CalculatorNet Promoter Score from your 0–10 survey counts. A/B Test Significance CalculatorIs your A/B result real? Z-test with p-value. Sample Size CalculatorHow many survey responses you actually need. Email Open Rate CalculatorOpen rate, click rate and CTOR from one campaign. Engagement Rate CalculatorER by followers and by reach — the influencer metric. Payback Period CalculatorHow long until an investment repays itself. NPV CalculatorNet present value of a cash flow series. IRR CalculatorThe annualized return your cash flows actually earn. Markup CalculatorCost → price via markup or margin — and why they differ.

Developer Tools

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HEX to RGB ConverterHEX ↔ RGB ↔ HSL with a live color preview. Pixel to REM ConverterPixels ↔ rem/em with adjustable root font size. Aspect Ratio CalculatorKeep proportions: solve missing width, height or ratio. Download Time CalculatorDownload/upload time from file size and speed. Subnet CalculatorCIDR → netmask, network, broadcast and host range. Password Strength CheckerEntropy and estimated crack time — checked locally. Base64 Encoder / DecoderEncode text to Base64 or decode it back. JSON Formatter & ValidatorBeautify, minify and validate JSON — with error locations. Hash GeneratorSHA-256 / SHA-1 / SHA-512 hashes, generated locally. Chmod CalculatorPermission checkboxes ↔ chmod octal (755, 644…). Cron Expression GeneratorExplain any cron expression in plain English. PPI CalculatorPPI, dot pitch and density from resolution + size.

Construction & Home

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Square Footage CalculatorRoom area in sq ft and m², with waste and cost. Concrete CalculatorSlab volume in m³/yd³ and pre-mix bags needed. Paint CalculatorLitres of paint from wall area, coats and openings. Tile CalculatorTiles and boxes needed for a floor or wall. Flooring CalculatorBoxes of flooring from area and pack coverage. Roofing CalculatorTrue sloped roof area from footprint and pitch. Brick CalculatorBricks for a wall, including mortar and waste. Fence CalculatorPosts, panels and rails from fence length. Gravel & Sand CalculatorGravel/sand/mulch volume and tonnage from area & depth. Staircase CalculatorSteps, rise and going from total floor-to-floor height. Wallpaper CalculatorWallpaper rolls from wall size and pattern repeat. Carpet CalculatorCarpet length and area from room size and roll width. Deck CalculatorDeck boards, joists and screws from deck size. Pool Volume CalculatorPool water volume in litres and gallons. BTU / AC Sizing CalculatorAC cooling capacity (BTU & kW) for a room. Electricity Cost CalculatorAppliance running cost per day, month and year. Construction Cost EstimatorRough build/renovation budget from area × rate.

Electrical & Engineering

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Ohm's Law CalculatorEnter any two of V, I, R, P — get the other two. Resistor Color Code CalculatorResistor color bands → resistance and tolerance. Wire Gauge CalculatorAWG ↔ mm², with a current-capacity guide. Voltage Drop CalculatorVoltage lost over a cable run, with % check. Power Consumption CalculatorWatts + hours → kWh per day/month/year and cost. LED Resistor CalculatorSeries resistor value and wattage for any LED. Solar Panel Sizing CalculatorSolar array size (kW) and panel count from usage. Battery Life CalculatorBattery runtime from capacity and current draw. Gear Ratio CalculatorGear ratio, output speed and torque from teeth counts.

Automotive

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Fuel Cost CalculatorTrip fuel cost from distance, consumption and price. Mileage CalculatorFuel economy in mpg, km/L and L/100km. Horsepower & Torque CalculatorConvert between horsepower, torque and RPM. Tire Size CalculatorDecode tire sizes and check speedometer error. Car Depreciation CalculatorCar value over time and total depreciation. EV Range CalculatorElectric car range from battery size and efficiency. EV Charging Time CalculatorCharging time from battery, charger power and level. Lease vs Buy CalculatorCompare total cost of leasing vs buying a car.

Everyday & Lifestyle

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Split Bill CalculatorDivide a bill with tip, evenly between people. Road Trip Cost CalculatorTotal trip fuel + tolls, split between passengers. Wedding Budget CalculatorSplit a wedding budget across the usual categories. Moving Cost CalculatorEstimate a house move: movers, van, distance. Dog Years CalculatorDog's age in human years — the science-based way. Cat Years CalculatorCat's age in human years (vet chart). Carbon Footprint CalculatorEstimate your annual CO₂ from key lifestyle inputs. Rainwater Harvesting CalculatorRainwater you can collect from your roof area. Party Food CalculatorHow much food to buy for a party, per person. Party Drinks CalculatorHow much beer, wine and spirits to buy for a party.

Cooking & Kitchen

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Recipe ScalerScale a recipe to any number of servings. Cups to Grams ConverterCups ↔ grams, correct for each ingredient. Oven Temperature Converter°C ↔ °F ↔ gas mark ↔ fan oven settings. Butter Conversion CalculatorSticks ↔ cups ↔ grams ↔ tbsp of butter. Coffee to Water Ratio CalculatorGrams of coffee and water for your perfect brew. Yeast Conversion CalculatorConvert fresh ↔ active dry ↔ instant yeast. BBQ Meat CalculatorHow much meat to grill per person for a BBQ.

Work & Pay

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Overtime CalculatorOvertime pay and total wages from hours and rate. Hourly to Salary ConverterHourly wage ↔ annual/monthly/weekly salary. Freelancer Rate CalculatorThe day/hourly rate you need to charge as a freelancer. Billable Hours CalculatorBillable revenue, utilisation and effective rate. PTO Accrual CalculatorPTO earned per pay period and banked total. Severance Pay CalculatorEstimate severance from service, salary and formula. Notice Period CalculatorNotice period and end date from length of service. Employee Cost CalculatorThe true cost of an employee, beyond salary.

Fun & Games

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Love CalculatorA light-hearted love-compatibility meter (for fun). Numerology CalculatorYour numerology life path number from your birthday. Chinese Zodiac CalculatorYour Chinese zodiac animal and element by birth year. Zodiac Sign FinderYour Western star sign from your birth date. Zodiac Compatibility CalculatorHow two star signs match, by element (for fun). Angel Number CalculatorThe traditional meaning of a repeating angel number. Biorhythm CalculatorYour physical, emotional & intellectual cycles today. Name Numerology CalculatorYour name's numerology number and meaning. Birthday Personality CalculatorA fun personality profile from your birthday. Moon Sign CalculatorEstimate your astrological moon sign by date & time.