dax for calculating sum PTD based on different columns

It cannot be a calculated column. Those never recalculate during use and ignore user selection.

A measure of = SUM(Table[Sales]) will work. If you put the site, Month, and Week in a visual and filter based on those, it will automatically calculate your values. Nothing fancy needed at all.

If you are trying to get a cumulative total, the correct way is to use a date table, but you can do it with your data.

PTD = 
VAR varCurrentSite = MAX('Table'[Site])
VAR varCurrentMonth = MAX('Table'[Month])
VAR varCurrentWeek = MAX('Table'[Week])
RETURN
CALCULATE(
    SUM('Table'[Sales]),
    FILTER(
        ALL('Table'),
        'Table'[Site] = varCurrentSite
            && 'Table'[Month] = varCurrentMonth
            && 'Table'[Week] <= varCurrentWeek
    )
)

Hi, Anonymous , you might want to try such a calculated column

PTD = 
SUMX (
    FILTER (
        Table1,
        Table1[Site] = EARLIER ( Table1[Site] )
            && Table1[Month] = EARLIER ( Table1[Month] )
            && Table1[Week] <= EARLIER ( Table1[Week] )
    ),
    Table1[Sales]
)