I'm trying to understand how Yahoo finance calculates the RSI intraday, what is the time frame, how many items in calculation, what is the price used, etc.

I did not find any documentation or posts about it, except for some suggesting it's a 14 elements with a varying time frame.

Will appreciate any response.

RSI is calculated the same way regardless of the time period. A 14 period RSI on daily data is 14 days. If you're looking at 5 minute bars, a 14 period RSI would cover 14 five minute bars.

RSI involves the ratio of total gains in the past N periods divided by the total losses in the past N periods. You can Google for the formula. The following might be of interest:

RSI formula doubts

• Thanks for responding, formula is clear to me, was just wondering what yahoo finance is using for input of time and prices when executing the calculation, is it prices of moving averages? high / low? in reference to time, it it 1 minute / 2 minute / when does the interval change and why?
– Y.S
Commented Oct 30, 2018 at 15:15
• Can you provide a link so I can see exactly what you're looking at? If you are asking about the high and low then the formula isn't clear to you. A gain (or loss) is the one day ROC, aka one day's close minus the previous day's close. RSI is the ratio of the exponentially smoothed moving average of N period gains divided by the absolute value of the exponentially smoothed moving average of N period losses. Here's an example (except that they don't do the exponential smoothing correctly. Commented Oct 30, 2018 at 15:22
• Thanks again,I will try to explain better, I want to use RSI for day trading indication, so I have 1 second-5 minute trades, and for that I want to build RSI within the same day (or short time interval in the day), obviously looking 14 days back will not help here, so If I choose any stock at Yahoo finance, E.g. BAC, you can see that the RSI is calculated, and it is actually being adapted as price shifts, but it's not clear to me what is the time / periods / price inputs. hope that answers your comment
– Y.S
Commented Oct 30, 2018 at 15:28
• If you create a spreadsheet with the RSI formula, it will calculate the embedded period selected. So if you drop daily data into it, it's a standard 14 day RSI. If you drop 5 minute data into it, it calculates a 14 period RSI on 5 minute data. The formula remains the same (unless you choose to look at a different N period length) and only the time period of the data changes. The same holds true with charting programs. Commented Oct 30, 2018 at 15:44