Free Online Calculators
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View all →String Tension Calculator — Tennis, Badminton & Racquetball
Find a recommended racquet string tension by sport, skill level, and string type — plus a restring-frequency helper for tennis, badminton, and racquetball.
Aspect Ratio Calculator — Find, Convert & Resize
Find the simplified aspect ratio from width and height, solve for a missing dimension from a target ratio, or resize proportionally without distortion.
Quilt Fabric Calculator: Yardage for Top, Backing & Binding
Calculate quilt fabric yardage for top, backing, and binding. Choose quilt size and number of fabrics — get yards per color, backing panels, and binding.
Cross Stitch Calculator: Fabric Size, Stitch Count & Floss
Cross stitch calculator: enter stitch count and fabric type, get finished size, buy size, hoop recommendation, floss skeins, and time estimate. Inches and cm.
education Calculators
View all (20) →Balance Equation Calculator — Chemical Equation Balancer
Balance any neutral molecular chemical equation instantly using the algebraic method. See the coefficients plus a step-by-step element-count check.
Kinetic Energy Calculator — Translational & Rotational KE
Calculate kinetic energy (½mv²) or rotational KE (½Iω²). Supports kg/lb, m/s/mph/km/h, and RPM conversion. Joules or foot-pounds output.
Molarity Calculator — Concentration & Dilution (M1V1=M2V2)
Calculate molarity from mass and molar mass, or solve any dilution variable with M1V1 = M2V2. Instant results for lab and homework chemistry.
Momentum Calculator — Collisions & p = mv
Calculate momentum (p = mv) plus perfectly inelastic and perfectly elastic collision outcomes, with kinetic energy checked before and after.
Torque Calculator — Force, Lever Arm & Power/RPM Solver
Calculate torque from force and lever arm at any angle, or solve for torque, power, or RPM given any two values. Metric and imperial units.
Ideal Gas Law Calculator — Solve PV = nRT
Solve PV = nRT for pressure, volume, moles, or temperature. Auto-converts °C/°F to Kelvin and matches R to atm, kPa, or mmHg.
Percent Yield Calculator — Actual vs Theoretical Yield
Calculate percent yield from actual and theoretical yield in grams or moles. Instant result plus a plain-language read on what your yield suggests.
Inequality Calculator — Linear & Compound, Step-by-Step
Solve linear and compound linear inequalities step by step. Automatic sign-flip handling on negative multiplication/division, plus correct interval notation.
Rational Expressions Calculator — Simplify, Add, Multiply, Divide
Simplify, add, subtract, multiply, or divide rational expressions with full factoring steps — domain restrictions are always shown, even when they cancel out.
engineering Calculators
View all (12) →Resistance Calculator — Ohm's Law, Series & Parallel
Solve Ohm's Law for V, I, or R, plus total series and parallel resistance for any number of resistors. Free instant calculator.
Quarter Mile Calculator: ET & Trap Speed Estimator
Estimate quarter-mile elapsed time and trap speed from weight and horsepower, or solve for the horsepower needed to hit a target ET.
Square Yard Calculator — Area Converter & Room Size
Convert square yards, feet, meters, and inches, or calculate area from length and width — plus carpet, turf, and flooring cost per square yard.
Unit Conversion Calculator — Amps, Torque, Pressure, Power
Convert amps to watts, ft-lb to joules/N·m, MPa/bar to PSI, kW to HP, and PSI to kPa — bidirectional, with exact NIST conversion factors.
Towing Capacity Calculator — Max Trailer Weight & Payload
Calculate your max trailer weight, payload capacity, and recommended tongue weight from your vehicle's GCWR, GVWR, and curb weight.
Voltage Drop Calculator — NEC Formula, Single & 3-Phase
Calculate voltage drop and percentage for any wire run using the NEC formula. Single-phase and three-phase, copper or aluminum, full AWG table.
Acreage Calculator — Land Area Converter & Parcel Size
Convert acres, square feet, hectares, and square yards, or calculate acreage from a rectangular parcel's length and width — plus a football-field comparison.
Power-to-Weight Ratio Calculator: hp/ton & W/kg
Calculate power-to-weight ratio for cars (hp/ton), cycling (W/kg with pro benchmark tiers), or general machinery (kW/kg). Instant results.
Chain Rule Calculator — Step-by-Step Derivatives
Calculate derivatives of composite functions using the chain rule. Picks outer and inner function, shows u-substitution steps, dy/du, du/dx, and final answer.
fashion Calculators
View all →finance Calculators
View all (49) →NPV Calculator — Net Present Value & Discounted Cash Flow
Calculate Net Present Value from an initial investment, discount rate, and multiple cash flow periods, with a year-by-year discounted cash flow table.
Basis Point Calculator — Convert bps, % and Decimal
Convert basis points to percent and decimal, then apply a bps change to a dollar value to see the exact impact on rates, fees, and balances.
Capital Adequacy Ratio Calculator — Basel III CAR
Calculate CET1, Tier 1, and Total Capital ratios against Basel III minimums and buffer thresholds. Built for banking students and finance professionals.
Dividend Reinvestment (DRIP) Calculator
Simulate dividend reinvestment quarter by quarter. See final shares, portfolio value, and income vs. taking the same dividends as cash.
Expense Ratio Calculator — Fee Drag & Future Value
See how a fund's expense ratio reduces your net return and future value over time, with a side-by-side comparison against a 0%-fee scenario.
Gratuity Calculator — Tip Amount & Bill Split
Calculate tip amount, total bill, and per-person split. Tips on the pre-tax subtotal when tax is entered, with service-context tipping guidance.
Prorated Rent Calculator — Actual Days vs Banker's 30-Day
Calculate prorated rent for a partial month using the actual days-in-month and banker's 30-day methods side by side, plus which states require which.
YTD Calculator — Investment Return & Earnings Tracker
Calculate year-to-date investment return (price or total return with dividends) or track YTD earnings with an annualized full-year projection.
529 College Savings Calculator — Growth & Superfunding
Project 529 plan growth from monthly contributions, plus a gift-tax exclusion and 5-year superfunding calculator for 2026 limits.
fitness Calculators
View all (12) →Swing Weight Calculator — Bat MOI & Racquet Estimate
Estimate baseball/softball bat swing weight and drop from weight and balance point, plus a tennis racquet swingweight range classifier.
Navy Body Fat Calculator — Circumference Method
Estimate body fat using the US Navy circumference method (neck, waist, height, plus hip for women). Instant %BF with fitness category.
Weight Loss Percentage Calculator — % Lost & Goal Tracker
Find your weight loss percentage, track progress toward a goal weight, and see pounds remaining, plus a healthy pace check using the 0.5-1%/week guideline.
Batting Average Calculator — AVG, OBP, SLG & OPS
Calculate batting average from at-bats and hits, plus OBP, slugging percentage, and OPS from a full stat line. Correct no-leading-zero display.
Activity Calorie Calculator — Walking, Running, Cycling
Estimate calories burned walking, running, cycling, or on the treadmill using MET values from the Compendium of Physical Activities. Enter weight and duration.
Army Body Fat Calculator — 2024 One-Site Tape Test
Estimate Army body fat using the official 2024 one-site tape method or the legacy 3-site formula. Checks against age-based standards.
ERA Calculator — Earned Run Average & WHIP
Calculate ERA from innings pitched and earned runs, with correct baseball innings notation (outs, not decimals). Includes bonus WHIP calculation.
FFMI Calculator — Fat-Free Mass Index & Natural Limit
Calculate FFMI and normalized FFMI from weight, height, and body fat %. See where you fall vs the ~25 natural genetic limit from the Kouri et al. study.
DOTS Powerlifting Calculator: Score Your Squat, Bench & Deadlift
Calculate DOTS and Wilks scores from your powerlifting total. Bodyweight-adjusted for fair comparison across all weight classes and sexes.
gaming Calculators
View all (13) →Cribbage Calculator — Hand & Crib Score Checker
Score any cribbage hand instantly. Enter 4 cards plus the starter and get every fifteen, pair, run, flush, and nobs point counted for you.
Balatro Calculator — Chips × Mult Score Breakdown
Calculate your Balatro poker hand score step by step: base Chips × Mult, card chip values, and flat vs. multiplicative joker bonuses.
Robux Tax Calculator — Marketplace Fee & DevEx Cash-Out
Calculate the 30% Roblox marketplace fee on item sales and convert Earned Robux to USD at the current DevEx cash-out rate.
Uma Musume Affinity Calculator — Bond Level Planner
Find how much bond a support card needs to hit the 40/60/80/100 friendship thresholds and roughly how many training sessions that takes.
D&D Calculator — Point Buy, Dice, Encounter & HP
D&D 5e (2014) point buy, dice average, encounter difficulty, and hit points calculators in one tool for tabletop players and DMs.
Minecraft Nether Portal Calculator — Coordinates & Frame Size
Convert Overworld and Nether coordinates with the 1:8 ratio, and check portal frame size and link search radius in Minecraft Java and Bedrock.
OSRS Combat Calculator — Combat Level, DPS & Prayer Drain
Calculate your Old School RuneScape combat level, weapon DPS, and prayer point drain time — three combat tools in one calculator.
Fantasy Football Points Calculator — Standard, Half & Full PPR
Calculate fantasy football points from a full stat line in Standard, Half-PPR, Full PPR, or custom scoring, with a passing/rushing/receiving breakdown.
OSRS Dry Calculator — Drop Rate & Streak Probability
Calculate your true drop chance in Old School RuneScape from drop rate and kill count, plus kills needed for 50/90/99% confidence. Includes item presets.
health Calculators
View all (30) →Adjusted Age Calculator — Corrected Age for Preemies
Calculate corrected (adjusted) age for a premature baby from birth date and gestational age at birth. See chronological vs. corrected age side by side.
Growth Percentile Calculator — BMI & Head Circumference
Find your child's CDC BMI-for-age or head-circumference-for-age growth percentile using the official LMS method. Boys and girls, birth to 20 years.
Menopause Age Calculator — Typical Range & Perimenopause Timeline
See where your age sits in the typical 45–55 menopause range, learn the perimenopause timeline, and get risk-factor context — not a personal prediction.
Odds Ratio Calculator — 2×2 Table with 95% CI
Calculate odds ratio and 95% confidence interval from a 2×2 table. Automatic continuity correction, Woolf's method CI, and plain-language interpretation.
DRI Calculator — Daily Reference Intake by Age & Sex
Find your daily RDA/AI for protein, fiber, vitamin C, vitamin D, calcium, iron, and potassium by sex, age bracket, and pregnancy/lactation status.
Caffeine Calculator — Content Tracker & Half-Life
Log drinks to track daily caffeine intake vs the FDA's 400 mg benchmark, or find how much caffeine remains in your system via the half-life formula.
Gestational Age Calculator — Due Date, Conception & Implantation
Calculate due date, conception date, and implantation window from your LMP using Naegele's Rule. See your current gestational age in weeks and days.
Water Fasting Calculator — Stage & Safety Guide
Find which physiological stage your planned water fast falls in, plus a prominent safety checklist and physician-supervision guidance for extended fasts.
AST/ALT Ratio Calculator — De Ritis Ratio
Calculate the AST/ALT ratio (De Ritis ratio) from your liver panel and see what the pattern typically suggests, alongside individual normal-range checks.
home Calculators
View all (21) →Fence Post Depth Calculator — Hole Depth & Diameter
Find the right fence post hole depth using the 1/3-length rule, your frost line, and the 12 in IBC minimum — plus hole diameter and concrete volume.
Concrete Bag Calculator — How Many Bags Do I Need?
Calculate how many 40, 60, or 80 lb bags of concrete you need for a slab, footing, or post — plus total weight and cost estimate.
Electricity Cost Calculator — What Does It Cost to Run?
Calculate the daily, monthly, and annual cost to run any appliance from its wattage, hours used, and electricity rate. Add devices for a household total.
Flooring Installation Cost Calculator — Laminate, Carpet, Rug Pad
Estimate laminate, carpet, and rug pad installation costs by room size and material tier, including the sq ft to sq yd carpet conversion.
Insulation Calculator — Attic R-Value & Blown-In Cost
Find your recommended attic R-value by climate zone, then calculate blown-in insulation depth and installed cost for fiberglass or cellulose.
Window Replacement Cost Calculator — By Material
Estimate window replacement cost by material (vinyl, wood, fiberglass) and insert vs. full-frame installation, with a low-high price range for your project.
Asphalt Driveway Cost Calculator — Install & Resurface
Estimate asphalt driveway cost by size, project type, and thickness. Compare new installation vs resurface/overlay pricing with a low-high range.
Furnace Size Calculator — BTU & AC Tonnage Estimator
Estimate furnace BTU/hr and AC tonnage from square footage, climate zone, and insulation quality — a rough pre-Manual J sizing check, not a replacement for one.
Tree Removal Cost Calculator: 2026 Price Estimate
Estimate tree removal cost by height, plus stump removal, difficult-access, and emergency premiums. 2026 US pricing ranges for budgeting.
lifestyle Calculators
View all →Anniversary Calculator — Years Married, Countdown & Gift Themes
Calculate exactly how many years you've been married, the days until your next anniversary, and the traditional and modern gift theme for that year.
Audiobook Speed Calculator — Listening Time by Playback Speed
Find your adjusted audiobook listening time at any playback speed, or the speed needed to finish a book in the time you have available.
Graduation Date Calculator — Find Your Expected Class Year
Calculate expected high school graduation year by current grade or birth date and state kindergarten cutoff, plus estimated college graduation year.
Hebrew Birthday Calculator — Jewish Calendar Date Finder
Convert your Gregorian birth date to the Hebrew calendar and find exactly when your next Hebrew birthday falls, using real lunisolar calendar math.
Travel Time Calculator — Drive Time & Flight Time
Calculate drive time or flight time instantly. Choose highway, city, or suburban speed presets, or set a custom cruise speed and flight buffer.
Days Until Calculator — Countdown to Any Date
Find out exactly how many days until any date, with weeks and months breakdown, day of the week, and support for multiple saved countdowns.
Speaking Pace & Reading Time Calculator
Estimate speech or presentation time from word count and pace, or find reading time for silent reading and reading aloud using research-based speeds.
Words Per Minute Calculator — Gross & Net WPM
Calculate your typing speed in words per minute from characters typed or word count, plus accuracy-adjusted Net WPM and a speed benchmark tier.
outdoor Calculators
View all →Bike Size Calculator — Road, Mountain & Hybrid Frame Fit
Find your bike frame size by height for road, mountain, and hybrid bikes. Cross-checks with the inseam formula and standover clearance.
Plant Spacing Calculator — Garden Bed Plant Count
Calculate how many plants fit your garden bed from length, width, and spacing. Compare square grid vs hexagonal spacing, which fits ~15% more plants.
Arrow Speed Calculator — IBO Speed Adjustment & KE
Estimate your actual arrow speed from your bow's IBO rating, draw length, draw weight, and arrow weight. Includes kinetic energy for bowhunting.
Arrow FOC Calculator — Front of Center for Archery
Calculate arrow Front of Center (FOC%) from length and balance point, or from individual components. Ratings for target, hunting, and extreme FOC applications.
Tarp Size Calculator: What Size Tarp Do I Need?
Calculate what size tarp you need for hay bales, flatbed trucks, pools, and ground cover. Recommends the nearest standard tarp size automatically.
pet Calculators
View all →Aquarium Substrate Calculator — Sand, Gravel & Aqua Soil Pounds
Calculate how many pounds of sand, gravel, or aqua soil your tank needs from length, width, depth, and density. Presets for common tank sizes.
Dog Food Calculator — Daily Portion by Weight & Life Stage
Calculate your dog's daily food portion in cups or grams using the veterinary RER/DER formula, weight, and life-stage activity level.
Horse Color Calculator — Coat Color Genetics Predictor
Predict horse coat color from genotype: base color, cream, dun, champagne, silver, grey, roan, and spotting patterns, with the Frame Overo lethal warning.
Animal Gestation Calculator — Dog, Cat, Cattle, Goat, Horse
Estimate a due date for dogs, cats, cattle, goats, or horses from the breeding date. Species-specific earliest/expected/latest gestation windows.
Chocolate Toxicity Calculator for Dogs
Estimate theobromine toxicity risk after your dog eats chocolate, by weight and chocolate type. Includes ASPCA Poison Control guidance.
Dog Age Calculator — Human Years by Breed Size
Convert your dog's age to human years using the AVMA breed-size method or the UCSD epigenetic DNA formula. More accurate than the outdated x7 rule.
Puppy Weight Calculator — Predict Adult Dog Weight
Predict your puppy's adult weight from current age and weight using size-category growth curves for toy, medium, large, and giant breeds.
Cat Coat Color Calculator: Kitten Genetics Predictor (Punnett Square)
Predict kitten coat colors from parent genetics using Punnett squares. Covers B, D, O, and A loci — black, chocolate, cinnamon, dilutes, and tortoiseshell.
Fish Tank Stocking Calculator: Inch-per-Gallon, Surface Area & Bioload
Calculate how many fish your aquarium can hold using 3 methods: inch-per-gallon, surface area, and bioload. Fresh and saltwater. 13 preset species.
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