Using Percently
Percently is a free tool for general arithmetic and learning.
Precision and assumptions
Results use browser floating-point arithmetic and are displayed with up to six decimal places. Very small nonzero results are shown in scientific notation. The percentage-change calculator uses a positive starting value. The discount calculator excludes tax, shipping, and other charges.
Check important calculations
The tools are intended to help with everyday calculations. Verify results before using them for decisions that require exact arithmetic or specialist advice.
Availability
Features and content may change. An internet connection is needed to load the site, and JavaScript must be enabled for the interactive calculators. Explanations and examples remain readable without JavaScript.