# Ruler

### From Roll20 Wiki

The Ruler tool lets you click and drag to measure distances on the table. While you measure, other players will see your measurement line so you can discuss what you're measuring.

By default, the ruler snaps to the grid while you measure. You can hold the Alt key while measuring to prevent it from snapping to the grid. This allows you to measure more precise distances, rather than in 1 unit increments.

## Changing Settings (GM only)

You can change ruler and grid settings for each page by accessing its Page Settings. Among other things, you can change the scale, the distance units (feet, meters, etc.), and how diagonals are measured.

There are four options for measuring diagonals:

1. **D&D 4E Compatible** is the default setting. This measures a diagonal move as 1 unit. This simplifies the counting of squares at the expense of realism.

2. **Pathfinder/3.5E Compatible** measures a diagonal move as 1.5 units (rounding down). Thus, when 1 unit equals 5ft, diagonal moves alternate between 5ft and 10ft increments (i.e. 5ft, 15ft, 20ft, 30ft, etc.). This is slightly more complicated to count, but models reality more closely.

3. **Euclidean** measures diagonals using the Pythagorean Theorem. A diagonal move equals about 1.414 units using this method. This is also called the "real distance" or "as the crow flies".

4. **Manhattan** measures a diagonal distance as the sum of its horizontal and vertical distances. Effectively, a diagonal move equals 2 units using this method. This is also called "Taxicab geometry" or "rectilinear distance".