Strike, expiry and premium

The three numbers on every option

• The strike is the fixed price in the contract. A call pays the amount by which the underlying settles above it; a put pays the amount by which it settles below it (see calls and puts). Each expiry has its own ladder of listed strikes, densest around the current price.
• The expiry is when the option settles. On Deribit, OKX and Bybit, options expire at 08:00 UTC on their expiry date, and venues list dailies, weeklies, monthlies and quarterlies side by side (see expiration cycles). The time left is usually given as DTE, days to expiry; BOSS shows it as whole days remaining, rounded down.
• The premium is what the option costs: paid by the buyer, received by the seller, up front. It is the only number of the three set by the market rather than written into the contract.

One contract, three conventions

A contract is the unit you trade. Its size, how much of the underlying one contract covers, differs by venue:

• Deribit: one BTC option contract covers 1 BTC.
• OKX: one contract of its coin-margined BTC options covers 0.01 BTC, so 100 contracts make 1 BTC.
• Bybit: order sizes are given directly in BTC, in fractional steps, with no separate contract multiplier.

BOSS converts every quoted size into coins, so a "1" in a liquidity column means 1 BTC on all three venues. Every per-contract figure on this site is for one unit of the underlying.

Premium in coin or in dollars

Deribit's and OKX's BTC options are coin-margined: their premiums are quoted in BTC, such as 0.0370 BTC. Bybit's are settled in stablecoins and quoted in US dollars. The strike is in dollars everywhere. To put everything on one scale, BOSS converts each coin premium into dollars using the underlying price the venue reports for that option, and shows every premium, payoff and breakeven in USD. The difference matters beyond display: a coin-denominated premium changes in dollar terms when BTC moves even if its BTC price doesn't (see inverse vs linear).

A worked example

A 30-day BTC call with a $105,000 strike, with the expiry's forward at $100,000. On Deribit it is quoted 0.0365 BTC bid and 0.0375 BTC ask.

• In dollars: bid 0.0365 × $100,000 = $3,650, ask 0.0375 × $100,000 = $3,750, mid $3,700.
• Buying 3 contracts at the ask costs 3 × $3,750 = $11,250, plus an estimated trading fee of 0.03% of the underlying per contract, 3 × $30 = $90 (the fee is capped at 12.5% of the option's price on Deribit, far above $30 here).
• That position covers 3 BTC. The same exposure on OKX is 300 contracts.
• At expiry, if BTC settles at $112,000 the calls pay 3 × ($112,000 − $105,000) = $21,000, a profit of $21,000 − $11,250 − $90 = $9,660. At $105,000 or below they pay nothing and the loss is the $11,340 paid.

What moves the premium

The strike sets how far the underlying must travel to pay (its moneyness); the expiry sets how long it has to get there; and implied volatility sets how far the market thinks it will go. Together they decide how the premium splits into intrinsic and time value. Premiums are always quoted as a bid and an ask, and the gap between them is a real cost (see bid-ask, slippage and fees).