Ratio Calc is a quick and easy tool for radio control car racers to use trackside. Knowing your final drive ratio (FDR) is very useful for comparison with other racers to determine if your car is geared correctly. You can also view your favourite information on Apple Watch. It lets you quickly select your car by filtering on manufacturer and model. Select your pinion and spur size and the FDR is displayed. Tyre diameter can also be entered to calculate your rollout. Ratio and roll out charts are also available which plot pinion and spur gear combinations to create very handy reference tables. - Save your favourite cars for quick access - Save notes and track name against your favourite cars - Share ratio/rollout charts - Download new cars from within the app - Select measurement units (imperial/metric) - Select your preferred gear pitch, alternative ratios in other pitches will be shown - Over 1600 cars/variants in the database