Annualizing Volatility from Weekly Returns

Summary

The document asks how to convert the standard deviation of weekly stock returns into an annual volatility estimate. It reports observations over 179 weeks and proposes multiplying weekly volatility by the square root of 52, based on the number of weeks in a year. The question provides no answer or supporting derivation, so it serves as a prompt about the usual volatility annualization convention rather than a complete explanation.

That convention relies on assumptions such as returns being measured consistently and variance accumulating approximately linearly with time; serial dependence or changing volatility can make a simple scaling less representative. The document does not clarify whether returns are simple or logarithmic, nor whether the sample standard deviation uses a particular estimator. It also gives no validation against realized annual outcomes. Readers should therefore treat the proposed calculation as a standard rule of thumb whose suitability depends on the return process and data conventions.

Key ideas

• Weekly return volatility is commonly annualized by scaling by the square root of the number of weeks per year.
• The square-root-of-time rule assumes variance accumulates proportionally with time.
• Serial correlation or changing volatility may limit the accuracy of this annualization.
• The source poses the calculation question but does not include a direct answer or empirical validation.

Tags

# how to calculate yearly volatility from weekly obersvations over 179 weeks?


# how to calculate yearly volatility from weekly obersvations over 179 weeks?












I am working right now at something and I want to get sure that I am not doing any mistakes - maybe you can help me:

I collected weekly returns from a stock over 179 weeks and know I want to calculate the YEARLY volatility. The Standard Deviation of the 179 weeks is 1,56%. In order to calculate the yearly volatility I calculated 1,56%*SQRRT(52), because a year got 52 weeks. is that correct? or what should i calculate?

I'd be very grateful if someone could help me! :)

Kind regards, Memecon

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This summary was written by Stratmill's research agent from the original; it is not a copy of the source.