SET50 Options Payoff and Break-Even
Calculate expiry payoff and break-even for long SET50 calls and puts using strike, premium, and multiplier, with a numerical table before costs.
By Kru Kook (Krittiya Khunabrimas)
Inputs to the formula
This example uses SET50 Index Options. TFEX information checked on 22 October 2026 lists a THB 200 multiplier per point, and the premium is quoted in index points. Check the current series specification before trading.
Let K be the strike, S the final settlement index, P the premium per point, and M the contract multiplier.
Long call payoff
Net expiry payoff per long call = [max(S − K, 0) − P] × M − costs
The expiry break-even is K + P. Before other costs, the buyer’s maximum loss is the premium paid, or P × M, if the option expires without value.
Assume K = 900, P = 10 points, and M = THB 200. The expiry break-even is 910 points and the premium paid is THB 2,000 per contract.
Long call payoff table
| Final settlement index S | Call value before premium | Net P&L per contract before other costs |
|---|---|---|
| 890 | 0 points | −THB 2,000 |
| 900 | 0 points | −THB 2,000 |
| 910 | 10 points | THB 0 |
| 930 | 30 points | +THB 4,000 |
These are expiry outcomes using the assumptions above. They exclude fees, brokerage, and the result of closing the option before expiry.
Long put formula and break-even
Net expiry payoff per long put = [max(K − S, 0) − P] × M − costs
The expiry break-even is K − P. Before other costs, the buyer’s maximum loss is premium × multiplier.
Using K = 900 and P = 10 points, the put break-even is 890. If the final index is 870, gross net payoff is [(900 − 870) − 10] × 200 = THB 4,000 per contract.
When this formula applies
This calculates value at expiry, not the option’s intraday trading price. Before expiry, premium is also affected by time, implied volatility, supply and demand, and other factors. Option sellers have different risks, and margin requirements can change with the position.
Read our options basics guide before studying multi-leg strategies.