A percentage calculator is an essential tool for swiftly computing various percentage-related calculations, such as determining what percentage one number is of another, calculating percentage increases or decreases, and finding the original number after a percentage change. For instance, to find out what percentage 25 is of 200, you divide 25 by 200 and then multiply by 100, resulting in 12.5%. Similarly, to calculate a 15% increase on a $50 item, multiply $50 by 0.15 to get $7.50, and then add this to the original price to get $57.50. These calculations are vital in various fields, including finance, retail, and everyday budgeting, making percentage calculators indispensable for accurate and efficient computations.