# How do I calculate the quarterly returns of a stock index?

I was reading an article and it stated something along the lines of (not accurate figures):

``````Quarter | Stock Index % Change In Quarter

Sep 2011 | 5.21

Dec 2011 | 4.69

Mar 2012 | 3.20

June 2012 | -5.30

Sep 2012 | 5.11

Dec 2013 | 1.40
``````

Year to date: 25%

My question is, how would I calculate the percentage change in quarter?

For example if I was to calculate the March 2012 quarter percentage change do I subtract the closing price of the stock market index at March 30th 2012 from the closing price December 30th 2011 divided by the closing value of the index at Dec 30th 2011?

Or should I be using the opening prices (and possibly different dates?)

Secondly, how would I calculate the return ("Year to Date") for this year? Do I take subtract today's closing price from the closing price of 31st Dec 2012?

``````(((NEW - OLD)/OLD) * 100) = % Change from OLD to NEW
``````

So for quarters

``````(((NewQuarter - PastQuarter)/PastQuarter)*100)
``````

So, if Q1's value was 10 and Q2's value was 25

``````(((25-10)/10)*100) = ((15/10)*100) = 150%
``````

For closing or opening prices, I would use closing prices. For instance, some used `Adjusted Close` or `Close` on `Yahoo Finance` (see this example of AAPL).

Added Note: In your example, for your example, you'll want to take the absolute value of the denominator (aka: divisor), so an Excel formula might look like the below example ...

``````=((NEW-OLD)/ABS(OLD))*100
``````

... where the new and old are cells.

• You can also use `=(NEW/OLD-1)*100` – Chris Degnen Nov 11 '13 at 19:37

Here's a few demo steps, first calculating the year to date return, then calculating the Q4 quarterly return based on the cumulative returns for Q3 and Q4.  It's fine to use closing price to closing price as return periods.