What a Circuit Breaker Is
A circuit breaker is a pre-defined price limit that, once hit, automatically pauses trading. India runs two layers of this mechanism: stock-level price bands that freeze a single scrip, and a market-wide circuit breaker that halts the entire equity and equity-derivative market when an index moves sharply.
The idea borrows from electrical engineering: just as a fuse trips to stop a surge, a market circuit breaker trips to stop a runaway price move. It does not change anyone's view on value; it simply buys time so buyers and sellers can absorb information instead of trading on panic.
- Stock-level price band — caps how far one stock can move in a day; halts only that stock.
- Market-wide circuit breaker — triggered by the Nifty 50 or Sensex; halts the whole market for a set duration.
Stock-Level Price Bands (2/5/10/20%)
Exchanges assign each stock a daily price band of 2%, 5%, 10% or 20%, applied symmetrically above and below the previous day's closing price. The band reflects the scrip's risk profile: tighter bands (2% or 5%) are used for stocks under surveillance or those prone to manipulation, while liquid index stocks typically carry no scrip-level band but remain governed by other checks.
Stocks in the derivatives (F&O) segment do not have a fixed daily price band; instead they use a wider operating range with a dynamic price-band relaxation mechanism. The band is always measured against the prior day's close, not the open or the intraday high.
Upper / Lower Limit = Previous Close × (1 ± Band %)
| Band | Typical use |
|---|---|
| 2% | Stocks under tight surveillance / high manipulation risk |
| 5% | Low-liquidity or watch-list scrips |
| 10% | Many small and mid-cap stocks |
| 20% | Default for most non-F&O stocks |
Upper Circuit vs Lower Circuit
When a stock rises to the top of its band it has hit the upper circuit; when it falls to the bottom it has hit the lower circuit. At an upper circuit there are usually only buyers and no sellers, so trades stop because no one will sell. At a lower circuit the reverse is true — only sellers, no buyers.
Hitting a circuit does not necessarily halt the stock for the day; trading can resume if orders appear on the opposite side at the limit price. A stock can sit "locked" in an upper circuit for several sessions in a row, which is common after very strong news or a low free-float situation tied to high promoter holding.
- Upper circuit — price capped at the band's top; pending buy orders cannot be matched.
- Lower circuit — price floored at the band's bottom; pending sell orders cannot be matched.
Market-Wide Index Circuit Breaker
Beyond individual stocks, SEBI mandates a market-wide circuit breaker that halts trading across all equity and equity-derivative segments nationwide. It is triggered by movement in either the BSE Sensex or the Nifty 50, whichever breaches a threshold first.
The breaker applies at three stages in either direction — 10%, 15% and 20% — measured against the previous day's closing index level. The trigger points are computed by the exchanges daily and rounded to the nearest tick. Once the move reverses or the halt ends, the market reopens through a 15-minute pre-open call auction that discovers a fresh equilibrium price before continuous trading resumes.
Trigger Levels and Halt Durations
The halt duration depends on both the level breached and the time of day it happens. The rules below follow SEBI's index-based market-wide circuit-breaker mechanism (per SEBI Circular CIR/MRD/DP/25/2013), applied by the NSE and BSE.
| Index move | Before 1:00 pm | 1:00 pm – 2:30 pm | After 2:30 pm |
|---|---|---|---|
| 10% | 45-minute halt | 15-minute halt | No halt |
| Index move | Before 1:00 pm | 1:00 pm – 2:00 pm | At or after 2:00 pm |
|---|---|---|---|
| 15% | 1 hour 45 minutes | 45-minute halt | Halt for rest of day |
A 20% move halts trading for the remainder of the trading day, no matter when it occurs. Each halt at the 10% and 15% stages is followed by the 15-minute pre-open call auction before normal trading restarts.
- 10% — short pause early or midday; ignored late in the session.
- 15% — long pause early, shorter midday, full close from 2:00 pm.
- 20% — market shut for the rest of the day at any time.
Worked Example: Calculating a Price Band
Suppose an illustrative small-cap stock, Acme Steel, closed yesterday at ₹500 and carries a 10% price band. The exchange sets today's limits as shown below (figures illustrative).
| Item | Value |
|---|---|
| Previous close | ₹500 |
| Price band | 10% |
| Upper circuit (500 × 1.10) | ₹550 |
| Lower circuit (500 × 0.90) | ₹450 |
Today the stock can trade only between ₹450 and ₹550. If strong earnings push it to ₹550, it locks in the upper circuit and no trade can print above ₹550 today — buyers pile up with no sellers. If a profit warning drags it to ₹450, it hits the lower circuit. Tomorrow the band re-bases on today's close: if it closes at ₹550, the next day's range becomes ₹495 to ₹605. Note that a price band only limits the per-day move; it says nothing about whether the stock is trading near its intrinsic value or its book value per share.
Why Circuit Breakers Exist
Circuit breakers exist to curb panic and contain disorderly price moves. A sharp fall can feed on itself: falling prices trigger stop-losses and margin calls, which force more selling. A halt interrupts that loop and gives the market a cooling-off window to digest information rather than react to fear.
- Give investors time to absorb new information calmly rather than trade on rumour.
- Slow down feedback loops from stop-losses, margin calls and algorithmic selling.
- Restore orderly price discovery via the pre-open auction when trading resumes.
- Protect retail participants from extreme intraday swings driven by thin liquidity.
Circuits are a pause, not a verdict on value. After the halt, the same fundamentals apply — your read on P/E ratio and the business does not change just because trading stopped for 45 minutes.