How to calculate column value as summation of all previouse values

This is the demonstration of how to calculate a column value that depends upon sum of all previous values in that column. For example check following two tables
Actual Data:

ProductId	Name	Quantity
1	Product A	10
2	Product B	10
3	Product C	10

Required Output:

ProductId	Name	Cal Quantity
1	Product A	10
2	Product B	20
3	Product C	30

SQL Server Query:

SELECT P.ProductId, P.Name, SUM(PC.Quantity) AS Cal Quantity
FROM Products AS P LEFT OUTER JOIN Products AS PC
ON PC.ProductId <= P.ProductId
GROUP BY P.ProductId, P.Name