Ratio Calculator - Proportion

Proportions Calculator is a simple tool for calculating proportions. Just enter any three values and the program will find the fourth. Use it for resizing images and videos, finding tip amounts, calculating sales tax, scaling recipes, converting currency, or anything where proportions are used.
Features
* Any value can be the unknown
* Each entry can be cleared individually
* All entries can be cleared at one time
This App calculates proportions (direct or indirect), also known as "rule of three" by entering three known values and hitting "Calculate". The App will calculate the missing value for you!
A history of calculated values is kept and can be managed within the App.