WHAT IS BETA, AND HOW DO YOU ACTUALLY GET ONE?
Beta measures how much a share moves when the whole market moves. Beta 1 means it moves with the index; 1.5 means it swings half again as hard; 0.7 means it is steadier. It is the one input that turns a market-wide risk premium into this company's cost of equity — so a guessed beta quietly makes the entire valuation a guess. Below you will compute one from real data.
Get the index history from NSE
Go to nseindia.com → Market Data → Indices → Historical Data. Choose NIFTY 50, set the period to 3 years, and download the CSV. The Nifty 50 is the right benchmark for most Indian companies; use Nifty 500 only if the company is genuinely small-cap.
Why 3 years: long enough for the relationship to be real, short enough that the company is still the same business. 5 years is also defensible; 1 year is noise.
Get the share history the same way
nseindia.com → Equity → the company → Historical Data, same 3-year period. You need two columns from each file: the date and the closing price.
Keep the date column. It is tempting to delete it and paste just the two price columns together — that is exactly the mistake step 3 warns about. Use the close, not the open, high or low, and use the same one for both.
Line them up and convert prices into returns
In Excel put dates in column A, index close in B, share close in C — sorted oldest first. Then in D2 and E2:
The two NSE files will not line up on their own. A share is suspended, or has a special trading holiday the index does not, or was not listed for part of the period — so one file has rows the other does not. If you simply paste the two close columns side by side, from that point on you are comparing the share on 14 March with the index on 15 March. Beta then measures nothing at all, and it usually comes out too LOW, which quietly makes the company look safer than it is.
Do this instead: keep the date column from both files, use
=VLOOKUP or =XLOOKUP to pull the share close against each index date,
and delete every row where either side is blank. Then check: the first date, the last date and
the row count must be identical in both columns. Only then compute returns.E2 = (C3 - C2) / C2 ← share return
Fill both down. Monthly returns are the professional default — take the last trading day of each month rather than every day, because daily data on a thinly traded share is mostly noise and drags beta towards zero.
Two formulas, one answer
Beta is the slope of share returns regressed on index returns. Excel gives it two ways, and they are the same number — if yours disagree, the data is misaligned.
=SLOPE(E2:E37, D2:D37) ← (share returns, index returns)
=COVARIANCE.S(E2:E37, D2:D37) / VAR.S(D2:D37)
β = Cov(share, index) ÷ Var(index)
Order matters in SLOPE. Known-y comes first (the share), known-x second (the index). Reversed, you get the inverse relationship and a completely wrong beta.
Or paste the returns here and let this do it
Paste two columns — index return and share return — straight from Excel (tab, comma or space separated, one pair per line). Percentages or decimals both work.
Paste the returns, not the prices — and only rows where both dates matched. This tool cannot see your dates, so it has to trust that each line is one day (or one month) for both series.