Reference lines in Tableau - Cell-by-Cell Formula Trace

Sample Data

Monthly sales data for 5 months

Cell	Value
A1	Month
B1	Sales
A2	Jan
B2	100
A3	Feb
B3	150
A4	Mar
B4	120
A5	Apr
B5	130
A6	May
B6	170

Formula Trace

AVG([Sales])

Step 1: SUM([Sales])

Step 2: COUNT([Sales])

Step 3: AVG([Sales]) = SUM([Sales]) / COUNT([Sales])

Cell Reference Map

    A       B
1 Month   Sales
2 Jan     100
3 Feb     150
4 Mar     120
5 Apr     130
6 May     170

[Sales] values are from B2 to B6

Reference line uses the Sales column values from cells B2 to B6

Result

    A       B       C
1 Month   Sales   Reference Line
2 Jan     100     ----------------
3 Feb     150     |              
4 Mar     120     |  Average = 134
5 Apr     130     |              
6 May     170     ----------------

The reference line is drawn at the average sales value 134 across the months

Sheet Trace Quiz - 3 Questions

What is the sum of sales used to calculate the reference line?

A 670

B 134

C 5

D 150

Key Result

Reference line in Tableau uses aggregation functions like AVG() to calculate a constant value across the axis