Free Online Calculator Tools
Finance, time, units, and more. Instant calculations without ads or sign-up. All logic runs directly in your browser.
All Calculator Tools
Percentage Calculator
Three calculation modes: X% of Y, X is what % of Y, and % change between two numbers. Instant results with formula explanation.
Aspect Ratio Calculator
Calculate and simplify aspect ratios from width and height. Scale dimensions while locking ratio. Common ratios reference table.
Unit Converter
Convert between units of length, weight, temperature, speed, and area. Instant bidirectional conversion with common unit presets.
Color Opacity Calculator
Pick a HEX color and an opacity level to get the equivalent rgba(), 8-digit hex (#RRGGBBAA), and CSS custom property. Live color swatch.
CSS Specificity Calculator
Calculate the specificity of any CSS selector. Breaks down IDs, classes, attributes, pseudo-classes, elements, and pseudo-elements. Compare two selectors.
Accurate & Transparent Formulas
Every calculator shows the formula used and works with standard financial and mathematical conventions. No black boxes — results you can trust.