Numbers percentage % calculators, relative percentage increase or decrease changes, increase or decrease numbers by value percentage

Tax calculator: add or extract tax (ie: VAT) from value

Convert numbers to (US) American English words text representation, write numbers out

Sales Tax Calculator: add or reverse calculate tax

Simple flat rate interest calculator on principal initial money borrowed, lent or deposited

Leap years, calculator: is it a leap year? What is a leap year? What is the previous and the next leap year after a certain year?