Free Online Tools, Fast & Private

Free online tools: percentage calculator, age calculator, temperature converter. Fast, private, no sign-up.

Percentage Calculator

Calculate percentages instantly — what is X% of Y, X is what percent of Y, and percentage increase or decrease between two numbers.

Age Calculator

Find out your exact age in years, months, and days from your date of birth, plus how many days until your next birthday.

Temperature Converter

Convert temperature between Celsius (°C), Fahrenheit (°F), and Kelvin (K) instantly. Type in one unit and all others update live.

Why use Sea Tools?

Every tool works instantly in your browser — no downloads, no sign-up, and no data sent to any server. Whether you are a student, developer, traveler, or online seller, these simple calculators and converters save you time.