Calculators — 39 Free Online Tools
Free online calculators for arithmetic, percentages, BMI, age, dates, tips and tiling. No signup, no ads, every result computed locally in your browser.
The calculators people come back to: dates, percentages, health metrics, and the estimating arithmetic behind a quote. The Date Calculator handles calendar arithmetic and the Percentage Calculator covers the increase, decrease and difference cases spreadsheets never did, while the Tile Calculator and Paint Calculator turn a room measurement into an order of materials instead of a guess.
Just one calculation? Use the Free Online Calculator for arithmetic, scientific functions, unit conversion, loan payments and BMI. Everything else in the collection is listed below.
Age Calculator - Months, Days, Birthday & Countdown
Free age calculator. Your exact age in years, months, days, hours and minutes, plus the next birthday countdown and milestone dates.
Area Calculator - Square Feet for Rooms & Walls
Room, floor and wall areas in square feet and square meters, plus paint gallons, wallpaper rolls and carpet yards. Free, no signup.
Baby Percentile Calculator
Baby Percentile Calculator on WHO growth curves. Weight, length and head circumference percentiles with z-scores, charts and corrected age for preemies.
Blood Pressure Calculator - Average & Stage
Free blood pressure calculator. Average a batch of readings, see your ACC/AHA stage, MAP and pulse pressure, plus a private log with 7 and 30 day averages.
Body Fat Calculator - Navy, YMCA & BMI Free
Free body fat calculator: US Navy, YMCA, BMI and Jackson-Pollock methods. Fat mass, lean mass, healthy ranges and target weight. Private, no signup.
BTU Calculator - Free AC and Heating BTU Estimator
Free BTU calculator. Compute room heat load for AC and heating with ceiling, sun, insulation, climate, occupancy and kitchen factors. Convert to tons.
Calorie & Macro Calculator - BMR, TDEE & Goals
Free calorie calculator. Your BMR, TDEE and macro split for weight loss, maintenance or muscle gain, using Mifflin-St Jeor.
Concrete Calculator - Free Slab, Footing & Bag Estimator
Free concrete calculator for slabs, footings, columns, and stairs. Get cubic yards, cubic meters, bag counts (40/60/80 lb), mix ratio breakdown, and waste.
Condom Size Calculator - Find Your Exact Fit
Free condom size calculator. Enter girth and length in mm, cm or inches to get your nominal width range and a fit verdict for any condom. 100% private.
Date Calculator - Days Between Dates & Date Arithmetic
Free online date calculator. Calculate days between dates, add or subtract days/weeks/months/years from any date, and compute business days. 100% private.
Days Until Calculator - Countdown to Any Date
Free days until calculator. Countdown to any date: Christmas, birthday, holiday, or event. See how many days, hours, minutes left. No signup required.
Dog Age Calculator - Dog Years to Human Years
Free dog age calculator. Convert dog years to human years with AVMA + UCSD formulas. Breed presets, life stages, chart. No signup, private.
Due Date Calculator - Ovulation, LMP & IVF
Free due date calculator. Work out your due date from LMP, conception date or IVF transfer, with ovulation and fertile-window dates.
Electricity Cost Calculator - kWh Rate, Bill, Appliances
Price every appliance on your electric bill from your own kWh rate. Daily, monthly and yearly cost per device, in your browser, free.
Engagement Rate Calculator - Multi-Platform Social Media
Free engagement rate calculator. 6 platforms (IG/TikTok/YT/X/FB/LI), 3 formulas, 5 tier benchmarks, weighted engagement. No signup.
Fraction Calculator - Add, Subtract, Multiply & Divide
Free fraction calculator. Add, subtract, multiply, divide fractions. Simplify, convert mixed numbers, compare fractions. Step-by-step solutions. No signup.
Free BMI Calculator - Body Mass Index Checker
Free BMI calculator to check your body mass index. Metric and imperial units, instant results with health category. No signup required.
Free Online Calculator - Scientific, Percent, BMI & Loan
More than a phone keypad: scientific functions, percent, loan payments and BMI in metric and imperial units. Free to use, no signup.
Free Tile Calculator - Floor, Wall & Pattern Estimator
Free tile calculator with multi-room aggregation, 5 patterns, box optimization, grout and thinset estimator, waste factor. 100% private.
Free Tip Calculator - Quick & Easy Restaurant Tip Tool
Free tip calculator for restaurants. Calculate tip amount, split bills, and see per-person cost. Works offline, no signup required. Instant results.
GPA Calculator - 4 Scales, Semester, Cumulative & Target
Free GPA calculator with 4 scales, unlimited semesters, prior GPA integration, a target GPA planner, and Honors, AP and IB classes.
Grade Calculator - Weighted Average & Final Exam
Free grade calculator. Calculate weighted average grade, what you need on the final exam, and GPA. No signup, 100% private browser tool.
Graphing Calculator - Roots, Area & Fit
Free graphing calculator. Plot functions, polar, parametric and implicit curves, then get roots, turning points, area between curves, integrals and R2.
Heart Rate Zone Calculator - 5 Zones by Age
Free heart rate zone calculator. Enter your age to get all five training zones in bpm, compare four max HR formulas, and find your personal Zone 2 range.
Math Calculator - Polynomial, Matrix, Prime Factor
Free math calculator. 6 modes: polynomial factoring, prime factorization, GCF/LCM, matrix (det/inv), quadratic formula, sequence. Step-by-step. No signup.
P-Value Calculator - Hypothesis Test & Z, T, Chi-Square
Free p-value calculator. Run z-test, t-test, chi-square, regression and confidence intervals. Exact p-values, step-by-step. No signup, 100% private.
Paint Calculator - Free Wall, Room & Trim Estimator
Free paint calculator. Multi-room wall area, doors and windows subtraction, 6 paint types, 5 surface textures, multi-coat, primer, ceiling, trim, waste.
Percentage Calculator - Find %, Increase, Decrease
Free percentage calculator online. Calculate X% of Y, increase/decrease, reverse percentage, and add/subtract percent. Instant results, no signup.
Poker Odds Calculator - Texas Hold'em Equity
Free poker odds calculator. Exact hand-vs-hand equity by full enumeration, not Monte Carlo. Board cards, up to 3 players, call/fold helper. No signup.
PTO Calculator - Accrual & Balance
Free PTO calculator. Project your paid time off balance on any date from your pay schedule, accrual cap and carry-over limit, and estimate a payout.
Roofing Calculator - Pitch Squares Shingle Bundles Free
Free roofing calculator. True roof area from pitch multiplier (1/12 to 18/12), squares, shingle bundles, underlayment, starter strip, ridge cap, drip edge.
Running Pace Calculator - Pace, Time and Distance
Free running pace calculator. Calculate pace, time, or distance for any race. Generate splits, predict race times with Riegel formula, convert pace units.
Salary Calculator - Free Online Hourly to Annual Converter
Free salary calculator. Convert hourly to annual, monthly, biweekly, weekly pay instantly. Calculate overtime and unpaid time adjustments. No signup, 100%.
Sleep Calculator - Optimal Bedtime & Wake Up Time
Free sleep calculator. Find your ideal bedtime or wake-up time based on 90-minute sleep cycles. Wake up refreshed, not groggy. No signup, 100% private.
Solar Sizing Calculator
Free solar sizing calculator. Estimate solar panel array size and battery storage from monthly kWh use and peak sun hours. Private browser math, no signup.
Speech Time Calculator - Words to Minutes and Time
Free speech time calculator. Convert words to minutes and seconds at standard speaking rates (100-238 wpm). Paste text, set WPM, add pauses. No signup.
Statistics Calculator - Mean, Median & SD
Free statistics calculator. Compute mean, median, mode, standard deviation, variance, quartiles and z-scores step by step. No signup, 100% private.
Time Calculator - Add, Subtract Hours, Minutes & Seconds
Time between two times, add or subtract hours and minutes, convert hours to decimal and sum several periods. Overnight rollover, breaks, free.
Work Hours Calculator - Free Time Card & Timesheet
Free work hours calculator. Calculate weekly time card hours, overtime, break deductions, and pay. Supports 12h/24h format. No signup, 100% private.
Frequently Asked Questions
4 Q&AHow many free calculators are available?
There are 39 free online calculators: age calculator, area calculator, baby percentile calculator, blood pressure calculator, body fat calculator, btu calculator, calorie & macro calculator, concrete calculator, condom size calculator, date calculator, days until calculator, dog age calculator, and 27 more. All run locally in your browser with no signup, no ads, and no data transmission.
Are the calculator results accurate for medical, financial, or legal decisions?
Results are produced by standard, well-tested formulas (BMI = kg/m^2, age in calendar units, percentage = part/whole * 100, etc.) and are appropriate for everyday use. They are not a substitute for advice from a licensed medical, financial, or legal professional.
Do the calculators send my numbers to a server?
No. Every calculation runs entirely in your browser using JavaScript. Nothing is uploaded, logged, or stored. Closing the tab clears all input.
Can I use these on a phone or tablet?
Yes. All 39 calculators are touch-friendly, use a single-column layout on small screens, and work offline once the page has loaded once.
How to Use These Calculator Tools
guideEvery calculator tool below runs entirely in your browser — no signup, no upload, no watermark. To find a specific tool, type a name, keyword, or scenario into the search box and the list filters instantly. Popular calculator tools are linked in the summary at the top; click any card or link to open the tool and follow the on-screen instructions. Hover any tool card to read its full description, then click its name or button to open it.