Model and input conventions
The per-unit expression is terminal price minus acquisition price, plus the put payoff, minus the call payoff, minus the put premium plus the received call premium. The put strike must be lower than the call strike. After multiplying by quantity and subtracting fixed costs, the result has a lower terminal plateau and an upper plateau. Their heights depend on acquisition cost and net premium, not just on the two strikes.
Worked numerical example
For an acquisition at 100, a bought 90 put costing 4 and a sold 110 call receiving 3, the net option debit is 1. With one unit and no fees, the floor P&L is −11 and the ceiling is +9. A terminal price of 101 breaks even. At 85 the put offsets further stock losses; at 120 the short call offsets further stock gains.
Read the scenario table
Use the scenario table to inspect each component at the put strike, between the strikes and at the call strike. The terminal floor and cap are exact within the chosen payoff convention; they are not predictions of execution prices. Changing the initial acquisition value shifts total P&L without changing option intrinsic payoffs, which is useful when comparing a new collar with an older holding’s cost basis.
Where the model stops
Equal option premiums do not make the entire position free or eliminate risk. Fees can remain, the underlying still requires capital, and the floor can be below acquisition cost. The calculator assumes European-style cash settlement and does not model early assignment, collateral calls, premium funding or rolling the collar to later expiries. A protection gap can arise whenever real quantities or contract underlyings differ.