The Tehran Stock Exchange had a powerfully green session on Monday, 12 Mordad 1405 (3 August 2026). Yet the size of that day comes to three different numbers depending on which index you read: the free-float index rose 2.27 percent, the headline index TEDPIX rose 2.39 percent, and the equal-weight index rose 2.50 percent. None of the three is wrong, and all three measured exactly the same market in the same session.
The 0.23 percentage point gap between the highest and the lowest of those numbers is the product of one variable that is almost never read off the daily board: the free-float percentage. That single figure determines three things at once, a stock's weight in the index, the amount of money it takes to move its price, and how quickly a trading queue closes in it.
Background: what free float is, and why it produces three indices
Free float is the portion of a company's shares genuinely available to trade, the part not locked up in the hands of major and strategic shareholders. When a state holding company, a pension fund or a strategic owner holds 89 percent of a company, the market is effectively trading the remaining 11 percent. The company is the same size; the thing being bought and sold is not.
The three indices that gave three answers on Monday are three different responses to a single question: how large a share of the market average should each stock carry? The equal-weight index gives every symbol the same weight and ignores company size, so a small company moves it as much as the largest listed bank does. TEDPIX takes its weights from each company's total market capitalisation. The free-float index takes its weights from the floating portion alone.
Monday's own data proves the distinction. If TEDPIX were also weighted on the floating portion, its number would have had to match the free-float index exactly. Instead the two diverged by 0.12 percentage points in that same session, and that gap is what tells you two different weighting bases sit behind them.
The ordering of the three numbers is itself the news. The equal-weight index was highest and the free-float index lowest. That means the day's gain was not spread evenly across stocks: smaller names outran the average, and among the heavyweights the ones with less free float rose more.
To see how unstable that arrangement is, put two consecutive sessions side by side. On Sunday, 11 Mordad 1405 (2 August 2026), TEDPIX rose 1.96 percent to 5,154,059 points while the equal-weight index rose 1.51 percent to 1,461,309, leaving the headline index 0.45 percentage points ahead. The next day the two swapped places. A week earlier, on Saturday, 10 Mordad 1405 (1 August 2026), TEDPIX fell 0.4 percent while the equal-weight index set a record close in the same session, a fourth straight session of small-cap leadership recorded in our report on TEDPIX falling while the equal-weight index set a record.
The numbers of Monday, 3 August 2026
| Index | Weighting basis | Session close | Day's gain |
|---|
| Equal-weight index | Same weight for every symbol | 1,497,819 points | +2.50% (36,511 points) |
| TEDPIX (headline) | Total market capitalisation | 5,277,352 points | +2.39% (123,295 points) |
| Free-float index | Market value of the floating shares | 6,723,448 points | +2.27% (149,220 points) |
Now the hidden variable itself. The table below gives the free-float percentage of nine index heavyweights, as published on the capital market information platform on Tuesday, 13 Mordad 1405 (4 August 2026).
| Symbol | Company | Free float |
|---|
| Shepna | Isfahan Oil Refining | 42% |
| Vabmellat | Bank Mellat | 38% |
| Khodro | Iran Khodro | 38% |
| Foolad | Mobarakeh Steel of Isfahan | 36% |
| Fameli | National Iranian Copper Industries | 34% |
| Fars | Persian Gulf Petrochemical Industries | 28% |
| Kagol | Gol-e-Gohar Mining and Industrial | 23% |
| Shasta | Social Security Investment Company | 13% |
| Hamrah | Mobile Telecommunication Company of Iran | 11% |
The two ends of that table are almost four times apart. Two stocks that both carry index weight and both trade on the same board are, in terms of how much stock can actually be bought, two entirely different creatures. Daily prices are on the equity market prices page.
One day, two stocks, two completely different depths
The best test of that claim is two stocks that reached almost the same price outcome on Monday. Mobile Telecommunication Company of Iran and Isfahan Oil Refining both closed at the ceiling of their permitted band that day, and the low and the high of their session were a single number, meaning both traded the whole session at one price. Behind that identical outcome stood two markets of very different size.
| Measure (Monday, 3 August 2026) | Mobile Telecom (Hamrah) | Isfahan Oil Refining (Shepna) |
|---|
| Free float | 11% | 42% |
| Closing price | 6,760 rials | 10,920 rials |
| Day's gain | +2.89% | +2.92% |
| Volume | 55,170,407 shares | 421,024,807 shares |
| Number of trades | 574 | 9,665 |
| Traded value | 37 billion tomans | 460 billion tomans |
| Price to earnings (estimated EPS) | 6.2 | 6.0 |
Two stocks with nearly identical price to earnings ratios, 6.2 and 6.0 on the estimated earnings per share shown on the board, and nearly identical daily gains. Yet Isfahan Oil Refining recorded roughly 17 times the number of trades and about 12 times the traded value. Judged on the valuation ratio alone, the two looked like the same thing. To anyone trying to get in or out, one of them had a 460 billion toman market that day and the other a 37 billion toman one. Where the standard valuation tools break down is covered in a low price to earnings does not always mean cheap; free float is the layer those tools do not measure.
Drivers: why a low float builds queues
The ceiling on available supply is lower. In a stock where 89 percent of the shares sit locked with major holders, the total that could possibly be sold in one session is small from the outset. Demand that a high-float stock absorbs easily instead runs into the top of the permitted band in a low-float stock, and stops there.
Less money is needed to move the price. This is the same coin turned over. When the tradable daily volume is small, so is the sum required to carry the price to the ceiling. On Monday, 37 billion tomans was enough to lock Mobile Telecommunication at its ceiling; the same job in Isfahan Oil Refining took 460 billion tomans.
A single large buyer has an asymmetric effect. An order of a fixed size swallows a larger share of available supply in a low-float stock. That is why one fund or one institutional buyer can move the board in a low-float name while the same sum leaves no visible mark in a high-float one.
Then it reaches the index. Each stock's weight in the free-float index comes from the floating portion, not the whole company. So a name like Mobile Telecommunication, with a large market capitalisation but an 11 percent float, occupies more room in TEDPIX than it does in the free-float index. When such names run greener than the rest, TEDPIX pulls ahead and the free-float index falls behind. That is precisely what happened on Monday.
We reported the end of this chain last week from the outcome side: a stock locked at its ceiling displays a price at which a large share of its would-be buyers never traded. The same session produced a matching case in the tape, set out in our report on buyer power giving two opposite answers in one session.
Outlook
What can be said about the sessions ahead is a description of the mechanism, not a price forecast. The float percentage is not a fixed number: it rises when major shareholders sell into the market and falls when stock gathers back in their hands, and every change shifts that stock's weight in the free-float index. As long as the distribution of float across the market stays this uneven, the gap between the three indices will keep recurring; which one leads in the next session depends on where demand goes, and that cannot be inferred from today's data. Domestic markets are closed today, Tuesday 13 Mordad 1405 (4 August 2026), for Arbaeen, so the first test of this arrangement is the reopening session. The Monday market pulse carries the session in full.
Conclusion
On Monday, 3 August 2026, the Tehran bourse had a green day and three official numbers for the size of it, 2.27 to 2.50 percent, and their difference is not measurement error but a difference of weighting basis. This matters because free float decides both how much your stock is seen in each index and how many buyers face you on the day you want out. The one thing to remember: free float does not tell you what a share is worth, it tells you how much the number on the board can be relied on.
What to watch
- The daily gap between TEDPIX, the equal-weight index and the free-float index, which shows where each session's move was concentrated.
- The free-float percentage of every stock you hold, before any price to earnings comparison.
- Float changes after a block sale or a purchase by a major shareholder, which shift the stock's weight in the free-float index.
- The ratio of daily traded value to the value of the floating shares, as a simple gauge of a stock's real depth.
- Trade count against traded volume, which separates a board with many buyers from one built by a few large orders.
This report is a description of the mechanism and of published board data, and contains no buy or sell recommendation.
