AZ Tools

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Everyday

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Pet Age in Human Years

Convert your dog or cat's age into the rough "human-year equivalent" — using vet-recommended scales, not the old multiply-by-seven myth.

Everyday00

Caffeine Half-Life Calculator

Pick a coffee / tea / cola dose and see how much caffeine is still in your bloodstream now, in an hour, in six — and when it'll drop below the sleep threshold.

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Cooking Conversions

Convert between cups, tablespoons, teaspoons, millilitres, and fluid ounces — and weigh common ingredients in grams or ounces.

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Body Surface Area Calculator

Compute Body Surface Area in m² using five published formulas — Mosteller, Du Bois, Haycock, Boyd, Gehan & George — side by side.

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Salary Calculator

Convert between hourly, weekly, monthly, and yearly pay — with configurable work week and paid holidays.

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Math Expression Evaluator

Evaluate arithmetic expressions with the usual math functions — `sqrt`, `sin`, `log`, `pow`, `min/max`, and constants `pi`, `e`, `tau`.

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Number Formatter (Intl.NumberFormat)

Format a number the way each locale expects — `1,234,567.89`, `1.234.567,89`, `$1.23M`, `12 345 ₽` — and grab the matching JavaScript snippet.

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VAT / Sales Tax Calculator

Add tax to a net price or extract tax from a tax-inclusive price. Common VAT/GST/sales tax presets (5–25%).

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Time Card Calculator

Sum daily start/end times into a weekly total, subtract breaks, and split regular vs overtime. Optional hourly rate computes the paycheck.

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Pace Calculator

Compute running pace, finish time, or distance from any two of them. Presets for 5K, 10K, half, and marathon.

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Day of Year · ISO Week · Julian Day

Show day of year, ISO 8601 week, quarter, Julian day, Unix timestamp, leap-year status, and year progress for any date.

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Password Strength Checker

Estimate password strength via entropy and crack-time. Detects common passwords, sequences, and repeated characters. Nothing leaves your browser.

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Prime Factorization · GCD · LCM

Factor an integer into primes, list all divisors, and compute GCD and LCM of two numbers. Handles values up to ~10¹².

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ISBN Validator (ISBN-10 / ISBN-13)

Validate ISBN-10 and ISBN-13 checksums and convert between the two formats. Hyphens and spaces are handled.

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Water Intake Calculator

Estimate daily water needs from weight, activity, climate, and pregnancy/breastfeeding status — gives a target and a 4-block schedule.

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GPA Calculator (4.0 / 4.3 / 4.5 scales)

Compute your weighted GPA across courses on US 4.0, US 4.3 (+ grades), or Korean 4.5 scales. Tracks total credits and quality points.

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Coffee Brew Ratio Calculator

Pour-over, French press, AeroPress, espresso, cold brew — calculate coffee and water amounts from any ratio with method-specific defaults.

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Credit Card Validator (Luhn + Brand)

Validate a card number with the Luhn checksum, detect brand (Visa/MC/Amex/etc), and check expected length. Local, no network.

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IBAN Validator

Validate an International Bank Account Number — checks country code, length, and the mod-97 checksum. Supports 75+ countries.

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Macronutrient Calculator (Protein / Carbs / Fat)

Split your daily calories into grams of protein, carbs, and fat — IIFYM-style presets for balanced, low-carb, high-protein, or keto.

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Heart Rate Zones Calculator

Compute your 5 training zones from age and resting HR — pick max-HR formula (Tanaka / Fox / Gulati) and method (%MHR or %HRR / Karvonen).

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Body Fat % Calculator (US Navy Method)

Estimate body fat percentage from height, neck, waist (and hip for women) using the US Navy tape-measure formula.

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Pregnancy Due Date Calculator

Estimate your due date from LMP, conception date, or ultrasound — see current weeks and trimester.

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Discount & Sale Price Calculator

Calculate the sale price after a percent or fixed discount — plus tax, savings, and effective discount rate.

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Sleep Cycle Calculator (90-min cycles)

Find the best bedtime or wake time aligned to 90-minute sleep cycles so you wake up between cycles, not mid-deep-sleep.

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Calorie / BMR / TDEE Calculator (Mifflin-St Jeor)

Estimate your basal metabolic rate, daily calorie needs, and cut/maintain/bulk targets — Mifflin-St Jeor formula.

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Tally Counter

A click counter that survives a refresh — multi-counter, custom step, goal alert, and keyboard shortcuts.

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Online Notepad

Distraction-free scratch pad that autosaves to your browser — no account, no upload, no ads.

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Loan / Mortgage Calculator

Calculate the monthly payment, total interest, and full amortization schedule for any fixed-rate loan.

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Compound Interest Calculator

Project how a starting balance grows with regular contributions, your interest rate, and your compounding frequency.

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Age Calculator

Calculate exact age in years, months, days — and find your next birthday.

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BMI Calculator

Calculate Body Mass Index from height and weight, with a healthy range.

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Tip Calculator

Calculate the tip and split the total bill between people.

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Percentage Calculator

Work out percentages, what-percent, and percent change in one place.

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