The Simple GMP Formula
Grey Market Premium (GMP) is quoted as an absolute rupee value above the IPO issue price. The calculation is straightforward:
Expected Listing Price = Issue Price + GMP
And the expected gain percentage:
GMP % = (GMP ÷ Issue Price) × 100
Example Calculation
Let's say an IPO has:
- Issue Price: ₹150 (upper end of price band)
- GMP: ₹60
Then:
- Expected Listing Price = ₹150 + ₹60 = ₹210
- Expected Listing Gain = (60 ÷ 150) × 100 = 40%
Negative GMP
GMP can also go negative. If GMP is −₹20 with an issue price of ₹100:
- Expected Listing Price = ₹100 − ₹20 = ₹80
- This means a potential listing loss of 20%
Why Does GMP Change Daily?
GMP is driven by supply and demand in the informal grey market. It changes based on:
- Subscription numbers (Day 1, Day 2, Day 3)
- Market sentiment (Nifty/Sensex movement)
- Company fundamentals and analyst coverage
- Grey market operator activity
A GMP that starts at ₹80 on Day 1 can drop to ₹40 by listing day — always check the latest GMP before making decisions.
GMP vs Kostak
While GMP is the premium on the share, Kostak is the price paid for the entire IPO application. Kostak is fixed regardless of allotment — it's essentially an insurance premium for your application slot.
Bottom Line
GMP gives you a quick directional signal. But pair it with subscription data and the company's financials for a complete picture before deciding to apply — or sell on listing day.
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