Nifty vs Sensex: Constituents, Sector Weights, Lot Sizes and Tax

Nifty vs Sensex: The Core Difference in One Look

The Nifty 50 is the flagship index of the National Stock Exchange (NSE) and holds 50 of India's largest, most liquid companies. The Sensex (full name S&P BSE Sensex) is the flagship index of the BSE and holds 30 companies. Both are computed the same way, using free float market capitalisation, which means each company is weighted by the value of shares that are actually available for public trading, not promoter or government locked holdings. So a giant company where promoters hold 60 percent will count for less than its full size would suggest.

Because both indices select the same kind of company, the very largest businesses in India, they share most of their members. The result is that on a normal trading day the two indices move almost in lockstep. If the Nifty closes up 0.8 percent, the Sensex is very rarely more than 0.1 to 0.2 percent away from that. The differences that do exist come from the 20 extra mid sized large caps that Nifty holds but Sensex does not, and from small gaps in sector weights.

For a trader, the practical takeaways are about liquidity and contract size, not about which index is a better economic gauge. Nifty derivatives are far more heavily traded than Sensex derivatives, which usually means tighter bid ask spreads and easier fills. But Sensex options have grown popular for their own weekly expiry and a smaller per lot value, which suits accounts that want a lighter position.

Constituent and Sector Weight Table: The Real Side by Side

This is where most comparison articles wave their hands. Below is a concrete look at the heaviest stocks and the sector split. The exact weights shift every trading day with prices, and NSE and BSE rebalance the indices twice a year, so treat these as representative recent figures, illustrative only. Always confirm the live weight on niftyindices.com or bseindia.com before you size a trade around a single stock.

First, the top constituents. Notice how the same handful of names dominate both lists. The order and exact percentages differ slightly, but HDFC Bank, ICICI Bank, Reliance and Infosys are the engines of both indices.

Now the sector breakdown. This is the figure that actually explains why both indices behave the way they do. A heavy weight on financials means an RBI rate decision or a bank results day can move the entire index, while a relatively small weight on metals or pharma means those sectors barely register at the index level even on a big day for them.

The single most important line in that table is the first one. With roughly a third or more in financials, both Nifty and Sensex are, in practice, a concentrated bet on Indian banking. If you are long either index, you are mostly long HDFC Bank, ICICI Bank and SBI whether you intended to be or not.

Why the Two Indices Almost Never Diverge Much

People often ask which index is going up more on a given day, expecting a meaningful answer. In reality the gap is tiny. Around 28 of the 30 Sensex companies are also in the Nifty 50, and they are the largest 28, carrying the most weight in both. The 22 or so names that are in Nifty but not Sensex tend to be the smaller large caps and a few extra sectors, so they pull the Nifty only slightly away from the Sensex.

There are two main reasons a small gap can open up on a given day. First, different exact weights: if HDFC Bank has a great day and it is a bigger slice of the Sensex than of the Nifty, the Sensex can edge ahead. Second, the extra Nifty names: if those 20 odd additional mid sized large caps rally or fall as a group, the Nifty diverges a touch. Over a full year these effects can add up to a percentage point or two of difference in total return, which is why their long run charts look nearly identical but not exactly the same.

Worked Example: A Nifty Index Option Trade With Real Numbers

Since you cannot buy the index directly, here is a fully worked weekly option trade on the Nifty. All figures are illustrative and chosen to show the mechanics, not to predict or promise any outcome. Markets can move against you and options can expire worthless.

Assume the Nifty is trading at 24,500. You expect a bounce into weekly expiry, so you buy one lot of the 24,600 call at a premium of 80 points. The Nifty F&O lot size is 65, so your contract controls 65 units of the index.

• Premium paid: 80 points x 65 = Rs 5,200 (this is your maximum loss if the option expires worthless).
• Suppose by expiry the Nifty closes at 24,800. Your 24,600 call is now worth 200 points of intrinsic value.
• Gross gain per unit: 200 - 80 = 120 points. Across 65 units that is 120 x 65 = Rs 7,800 before charges.
• STT on options is charged at 0.15 percent of the intrinsic settlement value on exercised in the money options at expiry, plus the usual 0.15 percent on the sell premium for options sold before expiry. On a small single lot this is a few rupees to a few tens of rupees.
• Brokerage on a discount broker is typically a flat Rs 20 per order, so about Rs 40 for buy plus sell, plus GST at 18 percent on brokerage and exchange charges, plus tiny SEBI and stamp charges.
• Net profit after rounding all charges is roughly Rs 7,600 to Rs 7,700 on this illustrative trade.

Now the downside, which matters more. If the Nifty instead drifts to 24,500 or below at expiry, the 24,600 call expires worthless and you lose the entire Rs 6,000 premium plus the small buy side charges. That is the hard rule of long options: limited and known loss, but you can lose all of the premium. The same trade structure works on the Sensex, except the Sensex lot size is 20, so a comparable Sensex option lot controls fewer units and ties up a smaller rupee amount per lot.

How Taxes Actually Work on Index Trades

Tax treatment depends entirely on how you trade the index, and getting this wrong is a common and expensive mistake. There are two distinct regimes.

• Index futures and options (F&O): profit and loss is treated as non speculative business income and taxed at your normal income tax slab rate. You can set off expenses and carry forward losses, but you report it as business income, often needing a tax audit once turnover crosses the threshold.
• Index ETFs and the underlying stocks held in the cash segment: gains are capital gains. Short term capital gains (held 12 months or less) are taxed at 20 percent. Long term capital gains (held more than 12 months) are taxed at 12.5 percent, and only on the amount above Rs 1.25 lakh of long term gains in a financial year.
• On top of tax, every trade carries Securities Transaction Tax (STT), brokerage, GST on brokerage and exchange fees, SEBI turnover fees and stamp duty. These are small per trade but add up for active traders.

The practical point: if you are an active intraday or weekly options trader on Nifty or Sensex, your gains are business income at slab rate, not the friendlier capital gains rates. Plan for that when you size positions and keep clean records, because the income tax department now receives detailed trade data from the exchanges.

Expiry Mechanics: Weekly and Monthly

Both indices have a single weekly expiry and a monthly expiry, following the SEBI move that limited each exchange to one weekly expiry contract. Index options are European style, meaning they can only be exercised at expiry, not before, and they are cash settled, so no shares change hands. You simply receive or pay the rupee difference based on the index closing level.

On expiry day the settlement value is not the last traded price but a volume weighted average of the index over the final portion of the session, which prevents a single last second tick from deciding everyone's payoff. Weekly options decay fast in their last day or two because time value collapses toward expiry, which is why buying cheap far out of the money weekly options close to expiry so often ends in a total loss of premium. Sellers collect that decay but carry large risk if the index gaps.

• Weekly expiry: short dated, cheap premiums, very fast time decay. Popular but unforgiving for buyers.
• Monthly expiry: more expensive, slower decay, used for positional and hedging trades.
• All index options are cash settled in rupees. You never take delivery of an index.
• Settlement uses a weighted average of the index near the close, not just the final tick.

Which One Should You Actually Trade?

For most traders the honest answer is that it barely matters at the index level because the two move together. The real decision is about liquidity, lot value and your account size. Nifty derivatives are the most liquid index product in India, with deep order books and tight spreads at almost every strike, which matters most when you trade size or scalp. Sensex options offer a smaller per lot value and their own weekly expiry, which can suit smaller accounts and traders who want to spread risk across two expiry days in a week.

If you are investing rather than trading, the choice is even less consequential. A Nifty 50 index fund and a Sensex index fund will hand you almost the same long run return because they own almost the same companies. Pick on cost: compare the expense ratio and the tracking error of the specific fund or ETF, since a cheaper, tighter tracking fund will quietly beat a pricier one over a decade regardless of whether it follows Nifty or Sensex.

• Want maximum liquidity and the tightest spreads: lean Nifty.
• Want a smaller per lot rupee value to start: consider Sensex.
• Investing for the long run via a fund: choose on expense ratio and tracking error, not the index name.
• Trading a bank heavy view: remember Bank Nifty is a more concentrated way to express that than either broad index.

Common Mistakes Traders Make With Nifty and Sensex

• Assuming the two indices give different signals. They almost never do; chasing a tiny gap between them is noise.
• Forgetting the financials concentration. Being long the index on a bad bank day rarely works, no matter the broader trend.
• Treating F&O gains as capital gains. They are business income at your slab rate; this surprises many at tax time.
• Buying far out of the money weekly options near expiry and losing the full premium to time decay.
• Ignoring charges. STT, brokerage, GST and stamp duty quietly erode small, frequent trades.
• Mixing up lot sizes. Nifty is 75, Sensex is 10; sizing a trade with the wrong number distorts your risk badly.

Sources and Further Reading

For authoritative and up to date data, refer to NSE Indices (Nifty Indices) for live Nifty constituents and weights, BSE India for Sensex composition, NSE India for contract specifications and lot sizes, and SEBI Investor Education for current rules. Always confirm live weights, lot sizes, STT rates and tax rules on the official source before you trade. All numeric examples here are illustrative and are not a promise of any return.

Sources and Further Reading

For authoritative data and further reading on this topic, refer to NSE Indices (Nifty Indices), BSE India, NSE India and SEBI Investor Education. Always confirm current rules, rates and contract specifications on the official source before you trade.