Free Online Calculators & Tools

Find the ratio of any width/height and resize proportionally. Perfect for images and video.

Convert HEX color codes to RGB, HSL, and CSS values instantly.

Count characters with/without spaces, words, sentences, and paragraphs in real time.

Estimate GPT-4o and Claude token usage and API costs before sending prompts.

Calculate exact age from birthday in years, months, days, and weeks.

Convert Unix epoch timestamps to human-readable dates and back.

Convert numbers to Roman numerals and Roman numerals to numbers (1–3999).

Count days, weeks, months, and workdays between any two dates.

Calculate percentage increase or decrease between two values.

Convert Markdown to clean HTML with live preview. Supports all common syntax.

Transform CSV spreadsheet data into JSON format instantly.

Calculate tips and split bills between friends with custom percentages.

Estimate your federal and state income taxes for 2026. Free, instant results.