Calculate Return on Investment (ROI) to measure the profitability of an investment relative to its cost. Key metric for financial decision making.

Convert an hourly wage into an equivalent annual salary based on a standard work year. Helpful for job comparisons and income planning.

Calculate simple interest on a loan or investment over time. Useful for quick financial estimates without compounding complexity.

Estimate the number of years required to double an investment at a fixed interest rate. A classic mental math shortcut for investors.