The Ruler tool can be used to measure small objects or distances on a map.

## Measuring distances
Place the object next to the ruler and tap the screen to mark the end of the object. The exact measurement will be displayed at the top of the screen.

## Changing units
By default, the ruler will respect the distance units in Settings > Units. You can change the units of the ruler between centimeters and inches by tapping the units at the top of the screen.

## Measuring distances on a map
To measure distances on a map, you need to know the map scale. If it says something like 'Scale 1:62500', then you can use the 'Ratio' scale on the Ruler. If it says something like '1 inch = 1 mile' or has bars that can be measured, then you can use the 'Verbal' scale.

- **Ratio scale**: Enter the scale as shown on the map. For example, 1:62500 would become From = 1 and To = 62500.
- **Verbal scale**: Enter the scale as shown on the map. For example, 1 inch = 1 mile would become From = 1 inch and To = 1 mile.

Once the scale has been entered, measure the distance on the map, and the map distance will be displayed at the top of the screen.

## Calibration
Most devices correctly report the screen size, but you should compare Trail Sense to a physical ruler to make sure it is accurate.

If it is not accurate:

1. Open Settings > Ruler > Ruler scale.
2. Set the value to 1 and click 'OK'.
3. Open the Ruler tool and measure 1 inch or 1 centimeter on a physical ruler.
4. Open Settings > Ruler > Ruler scale.
5. Enter what Trail Sense measured for 1 inch or 1 centimeter and click 'OK'.

For example, if Trail Sense reported 1.5 cm when you measured 1 cm on the ruler, enter 1.5 as the ruler scale.

## Quick action
You can enable the Ruler quick action in the settings for the desired tab.

To use the quick action, tap the Ruler quick action button to display or hide the ruler. When active, tap the ruler to hide it.