Clear calculators with real explanations

Essentia keeps twenty practical tools and pairs each one with worked examples, formulas, limits, and FAQs so you can learn as you calculate.

Math & quantities

Percentage Calculator Percent of a value, percent change, reverse percent, and “what percent is X of Y”. Probability Calculator Coin flips, dice odds, combinations, and simple conditional chance with the formula shown beside the answer. Unit Converter Length, mass, temperature, volume, and speed conversions with exact factors explained. Math & Scientific Calculator Arithmetic, powers, roots, and common scientific functions in the browser.

Everyday money math

VAT / Sales Tax Calculator Add or remove a tax rate from a net or gross amount. Rates vary by country and product. Tip & Bill Split Split a bill across people with an optional tip percentage. ROI Calculator Return on investment from cost and gain, shown as ratio and percent. Loan Amortization Monthly payment and interest share for a fixed-rate amortizing loan.

Time & patterns

Timezone Converter Compare a moment across IANA time zones using your browser clock APIs. Date Difference Days between dates, add or subtract days, and calendar helpers. Cron Expression Helper Explain a five-field cron string in plain language. Regex Tester Test a JavaScript-style pattern against sample text and see matches.

Color & layout

Contrast Checker Check foreground and background contrast ratios against WCAG AA and AAA. Color Converter Convert between HEX, RGB, and HSL for design and CSS work. Aspect Ratio Calculator Scale width or height while keeping a ratio such as 16:9 or 4:3.