Calculators

Calculate exact age and day difference from birth date with timezone aware handling.

Flip a coin online with 3D animation, multi-coin mode, decision helper, and session statistics — powered by cryptographic randomness.

Unified countdown timer and stopwatch with up to 10 concurrent timer cards, natural-language input, serialized alarm queue, local restore, cross-tab sync, voice announcements, custom preset editor (drag-reorder, color-coded, shareable link), 15 ready presets (Pomodoro, Tabata, egg, ramen, meditation, meeting), multi-step engine, Web Audio bells, Wake Lock, fullscreen big display, and shareable URL. Timers run in the current browser with no login required and do not rely on a LittleOne Tools timer backend.

Calculate date differences, date offsets, business-day offsets, and lookup ISO week, quarter, leap year, lunar, zodiac, and solar-term details.

Find the day number for any date, reverse-lookup a day number to its date, and view a full year calendar table with progress bar, ISO week, and quarter info.

Calculate discount amount, sale price, and savings online.

Free online electronic signature pad: handwrite with mouse / finger / stylus, with Apple Pencil pressure, palm rejection, quadratic Bézier smoothing + velocity-responsive stroke width, stroke-level undo/redo (including undoable clear), three brushes (pen / marker / highlighter), three preset colors + custom. Export transparent PNG @1x/@2x/@3x, white-background JPG, or vector SVG (auto-trimmed bounding box with optional padding), copy to clipboard. Browser-local, no uploads, no login.

Check if a year is a leap year, list leap years in a range, with step-by-step rule verification and statistics.

Bidirectional conversion between Gregorian and Chinese lunar calendar (1900-2100). Four modes: single-day lookup (three-pillar Ganzhi, zodiac, lunar month names, precise solar-term times), 6×7 month grid (dual-labeled Gregorian + lunar + solar term + festival), batch conversion (multi-line paste or CSV / JSON upload, up to 1000 rows), and annual lookup of 18 lunar festivals + 24 solar terms. Handles leap-month disambiguation, .ics calendar download, and URL share links. Client-side computation, no app backend, no login.

Calculate X% of Y, find percentage share, reverse a percent, and measure percentage change.

Paste a list and one click covers name picking, prize draws and team grouping. Your data is not uploaded by the tool.

Free online reaction-speed self-test: Simple RT (tap when signal turns green), Choice RT (4-color choice response), and Go/No-Go (respond to green, not red). Configurable 3 / 5 / 10 / 20 trials, sub-millisecond timing with double-rAF baseline, false-start detection, MAD-based outlier rejection, median / SD / IQR statistics, and 6-tier neutral performance banding. Mobile-first (touch-action manipulation, full-screen tap zone, ≥72px targets), fully bilingual, keyboard-accessible, reduced-motion aware, optional 30-day local history, setup-only share URLs, PNG result poster export. Browser-local — no login, default no ad scripts, default no third-party analytics, no upload. For entertainment and personal reference only; not a medical, psychological, or neurological assessment, and not a substitute for professional driver-license testing.

Calculate tip amount, per-person split, and total bill online.

Local workday calculator: 5-market statutory holidays (CN/US/UK-EW/UK-SCT/UK-NIR/HK/JP, 2023-2027) + State Council 调休 / EO 11582 observed rule + custom holidays + 3 modes (count between dates / add-subtract / classify single day) + Excel NETWORKDAYS.INTL / WORKDAY.INTL compatibility + 17 weekend codes + 14-day calendar strip + fail-closed URL share. Mobile 44px touch-first. No login, default no ad scripts, default no third-party analytics.

Convert degrees, radians, gradians & more

Convert square meters, acres, hectares & more

Convert KB/MB/GB & KiB/MiB/GiB units

Convert between kg/m³, g/cm³, lb/ft³ and more

Local latitude/longitude format converter: smart `DD / DMS / DDM` parsing with `N/S/E/W`, sign handling, Chinese/English degree-minute-second symbols, order switching, and batch text conversion. Outputs signed DD, DMS, DDM, and GeoJSON Point side by side.

Convert joules, calories, kWh & more

Convert between L/min, m³/h, GPM, CFM and more

Convert between N, kgf, lbf, dyn and more

Convert between Hz, kHz, MHz, GHz, rpm and more

Convert L/100km, MPG, km/L & more

Convert meters, feet, miles & more

Convert watts, kilowatts, horsepower & more

Convert Pa, bar, atm, psi & more

Convert km/h, mph, knots, Mach & more

Convert Celsius, Fahrenheit & Kelvin

Convert seconds, minutes, hours, days & more

Convert between N·m, kgf·m, lbf·ft and more

Convert liters, gallons, cubic meters & more

Convert kilograms, pounds, ounces & more

Convert bra sizes between 6 systems + sister sizes

Convert ring sizes between US, UK, EU, JP, CN

Calculate PPI, PPCM, total pixels, aspect ratio, and physical dimensions from resolution and screen size.

Convert shoe sizes between US, UK, EU, JP, CN

Calculate tire dimensions and compare sizes

Free amortization calculator for generating a payment-by-payment schedule with principal, interest, remaining balance, and yearly summaries for a fixed-rate loan.

Free APR calculator for estimating APR, monthly payment, and net amount received on a fixed-rate installment loan using the loan amount, quoted annual rate, term, and required finance charges. Educational estimate only; not an official disclosure, lender quote, or financial advice.

Free auto loan calculator for estimating financed amount, monthly payment, total payment, and total interest using vehicle price, down payment, trade-in value, payoff, rebate, taxes, fees, annual rate, and term in months.

Estimate contribution margin, break-even units, and break-even sales from fixed costs, variable cost per unit, and selling price per unit. Educational estimate only; not financial, tax, legal, accounting, or pricing advice.

Estimate 2025 U.S. federal taxable income, income tax, and effective tax rate for standard-deduction ordinary-income scenarios. Supports four manually selected filing statuses and local-only calculation. Educational estimate only; not tax, legal, or financial advice, and not a filing tool.

Estimate equivalent buying power, cumulative inflation, and average annual change between two years using historical U.S. CPI-U annual averages. Educational estimate only; not financial, investment, tax, legal, or budgeting advice.

Free online loan calculator for estimating monthly payment, total payment, and total interest on a fixed-rate installment loan.

Mortgage calculator for principal-and-interest (P&I) estimates. Enter loan amount, annual rate, and term to estimate monthly payment, total payment, and total interest.

Free mortgage refinance calculator for comparing your current loan with a new fixed-rate refinance scenario. Estimate payment change, total payment, interest, refinance costs, and a simple break-even period for P&I only.

Estimate investment gain, total ROI, and annualized ROI from your total cost, final value, and holding period. Educational estimate only; not investment advice.

Estimate ending balance, total contributions, and interest earned from an initial deposit, fixed monthly contribution, time horizon, and estimated APY. Educational estimate only; not financial, investment, tax, legal, or accounting advice.

Estimate simple interest and total amount from a principal, annual rate, and time horizon. Educational estimate only; not for compound interest, APR, or amortized loans, and not financial, investment, legal, or tax advice.

Calculate adult BMI from height and weight using the standard formula and view the public reference category. For general information only; not medical advice or a diagnosis.

Estimate adult basal metabolic rate (BMR) from age, formula sex, height, and weight using the Mifflin-St Jeor formula. For general information only; not medical or nutrition advice.

Estimate adult body-fat percentage using Deurenberg BMI-based and U.S. Navy (Hodgdon-Beckett) formulas with metric and imperial inputs. Returns ACE category, fat mass, lean mass, FFMI, and a Jackson-Pollock ideal body-fat reference. For general information only; not medical advice.

Ishihara-style online self-test: 24 programmatically generated pseudoisochromatic plates automatically classify red / green / blue channel anomaly patterns and severity. Quick (10 plates) and standard (24 plates) modes; mobile-optimized; bilingual. Browser-local, no login, default no ad scripts, default no third-party analytics — results are not uploaded by the tool. For reference and self-understanding only; not a medical diagnosis. Consult an eye-care professional if you have concerns.

Calculate due dates from start date and offsets for business-day or calendar-day scenarios.

Estimate your ovulation date and fertile window from the first day of your last period and your average cycle length. For general information only; not medical advice, a diagnosis, or birth control.

Estimate adult TDEE from age, formula sex, height, weight, and activity level using the Mifflin-St Jeor formula and fixed activity multipliers. For general information only; not medical, nutrition, or training advice.

Compute n! (factorial), n!! (double factorial), and !n (subfactorial) with BigInt precision, digit counts, and trailing-zero analysis.

Compute the nth Fibonacci number, generate the first n terms, or check whether a number is Fibonacci. BigInt precision with golden-ratio convergence analysis.

Calculate the final exam score you need from your current grade, final weight, and target course grade.

Free online fraction calculator supporting arbitrary-operand add/sub/mul/div with integer powers. Natively parses mixed numbers, repeating decimals (0.(3)), percents, and Unicode fraction characters (½ ¼ ⅓). BigInt exact arithmetic with auto-reduce, simultaneous display of improper/mixed/repeating-decimal/percent/LaTeX forms, and step-by-step LCM/combine/GCD explanation plus pie-chart and number-line visuals.

All-in-one geometry calculator for 25 common 2D shapes and 3D solids — area, perimeter, volume, surface area. Reverse-solve from any known value, with parameter-responsive SVG diagrams, substituted formula steps, per-field unit conversion, and adjustable significant figures / π precision.

Factor integers into primes, list all divisors with factor pairs, and test primality — with step-by-step process and large number support.

Calculate GCD and LCM for multiple integers with Extended Euclidean Algorithm and Bézout's identity. Shows step-by-step Euclidean and prime factorization methods.

Calculate GPA from course credits and letter grades with weighted grade points and total credits.

Calculate weighted course grades from assignments, quizzes, midterms, and finals.

Local matrix calculator with multi-matrix expressions, exact fraction arithmetic, step-by-step teaching, LU/QR/Cholesky decompositions, 2×2/3×3 eigenvalues, and Excel/CSV/MATLAB/NumPy/LaTeX paste. No login, default no ad scripts, no upload.

Local maze generator: 3 algorithms (Recursive Backtracker / Prim / Kruskal), reproducible seeds, A4 printable with optional answer page, QR code for mobile sharing, daily challenge seed. Includes dead-end highlight, shortest-path solver, PNG/SVG export. No login, default no ad scripts, no upload.

Education-grade + research-grade descriptive statistics calculator: 13 core statistics (mean, median, mode, variance, SD, range, quantiles, IQR, ...) + 3 education modes (China high school / international / research) + denominator toggle (n-1 / n) + 3 SVG charts (histogram / box plot / QQ-plot) + normality tests (Jarque-Bera + D'Agostino K²) + 3-method outlier detection + multi-delimiter paste + 4-format export. Welford+Kahan compensated numerical core.

Local Sudoku generator and game with real 5-level technique-based difficulty (Easy/Medium/Hard/Expert/Evil), triple highlighting (row-col-box/same-number/selected), auto-pencil candidates, 4-stage progressive hints, local best times, daily puzzle, URL sharing, 200-step undo/redo, dark mode. Mobile-friendly 44px touch targets. No login, default no ad scripts, no upload, default no third-party analytics.

Enter 4 playing cards (A/J/Q/K letters or 1–13 numbers) and see every expression that makes 24. Features exact rational arithmetic (catches fraction solutions like 8÷(3−8÷3)), equivalence dedup, bracket-minimized display, custom target, random deal, and classic hard-case presets. Works on desktop and mobile.