How is the Y-Axis scale determined in the Resource/Activity Usage Profile

When viewing the Resource Usage Profile or Activity Usage Profile in Primavera P6, you may notice that the Y-axis scale is automatically determined by the software. But how exactly is this value calculated?

Let’s break it down.

The Y-axis scale depends on the Timescale setting — whether it’s set to week, month, or year. Based on this setting, Primavera identifies the maximum value (i.e., the tallest bar) in the chart.

Let’s say we have a simple project, and the highest bar in the usage profile shows 8 hours.

Primavera uses the following steps to determine the Y-axis scale:

1. Calculate a buffer above the max value:
   MaxY = Max × 1.2 = 8 × 1.2 = 9.6 hours
2. Divide MaxY into 6 intervals:
   Interval size = 9.6 / 6 = 1.6
3. Round the interval size:
   • Round up the leftmost digit of the interval size.
   • In this case, 1.6 rounds up to 2.
4. Recalculate the MaxY using the rounded interval:
   New MaxY = 2 × 6 = 12

So, the Y-axis will be labeled in intervals of 2, with a maximum value of 12.

Note:

• All calculations are done in hours, but the display may convert to days or other time units depending on your settings.
• The rounding rule is based on the leftmost digit. For example, if the calculated interval is 1200, Primavera will round it up to 2000.