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Category Investments & Stocks

Short Strike Price ($) The strike you sell

Long Strike Price ($) The strike you buy

Premium Received (per share, $) Credit from the short leg

Premium Paid (per share, $) Cost of the long leg

Number of Contracts Each contract = 100 shares

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About

A credit spread is a vertical options strategy where a trader sells one option and buys another at a different strike within the same expiration. The net premium received represents the maximum profit. The critical risk is miscalculating the maximum loss, which equals the strike width minus the net credit, multiplied by 100 shares/contract and the number of contracts. A 1-point error in strike selection on 10 contracts creates $1,000 of unplanned exposure. This calculator computes P_max, L_max, breakeven price, return on risk, and risk/reward ratio for both bull put and bear call configurations. It assumes European-style settlement at expiration and does not model early assignment risk or dividend impact.

Formulas

For a Bull Put Credit Spread, the key equations at expiration are:

P_max = C_net × 100 × N

L_max = (K_short − K_long − C_net) × 100 × N

BE = K_short − C_net

For a Bear Call Credit Spread:

P_max = C_net × 100 × N

L_max = (K_long − K_short − C_net) × 100 × N

BE = K_short + C_net

Return on risk and risk/reward ratio:

ROR = P_maxL_max × 100%

R:R = L_maxP_max

Where C_net = net credit received per share, K_short = short strike price, K_long = long strike price, N = number of contracts, BE = breakeven price, ROR = return on risk, R:R = risk-to-reward ratio. The multiplier 100 reflects the standard equity option contract size of 100 shares.

Reference Data

Parameter	Bull Put Spread	Bear Call Spread
Market Outlook	Neutral to Bullish	Neutral to Bearish
Short Leg	Higher strike put (sold)	Lower strike call (sold)
Long Leg	Lower strike put (bought)	Higher strike call (bought)
Net Premium	Credit received	Credit received
Max Profit	Net Premium × 100 × Contracts	Net Premium × 100 × Contracts
Max Loss	(Strike Width − Net Premium) × 100 × Contracts	(Strike Width − Net Premium) × 100 × Contracts
Breakeven	Short Strike − Net Premium	Short Strike + Net Premium
Ideal IV Environment	High IV (sell expensive premium)	High IV (sell expensive premium)
Theta Effect	Positive (time decay benefits seller)	Positive (time decay benefits seller)
Vega Exposure	Negative (benefits from IV drop)	Negative (benefits from IV drop)
Delta Range (typical)	0.20 - 0.40 short delta	−0.20 - −0.40 short delta
Typical Strike Width	1 - 10 points	1 - 10 points
Common DTE Target	30 - 45 days	30 - 45 days
Margin Requirement	Strike Width × 100 × Contracts − Credit	Strike Width × 100 × Contracts − Credit
Probability of Profit (rule of thumb)	60 - 80% (depends on delta)	60 - 80% (depends on delta)
Risk/Reward Guideline	Target ≤ 3:1	Target ≤ 3:1
Assignment Risk	Short put ITM near expiration	Short call ITM near expiration
Closing Strategy	Buy back at 50% profit	Buy back at 50% profit

Frequently Asked Questions

Wider strike widths increase both the net credit received and the maximum loss proportionally. However, the max loss grows faster than the credit. A 5-point wide spread might collect $1.50 credit with $3.50 max risk, while a 10-point spread on the same short strike might collect $1.80 but risk $8.20. The return on risk (ROR) typically decreases with wider widths. Most practitioners target strike widths between 2 and 5 points for optimal risk/reward balance.

Standard U.S. equity options represent 100 shares per contract. A net credit of $0.75 per share translates to $75 per contract (0.75 × 100). Mini options (10 shares) and index options with different multipliers exist but are uncommon. This tool assumes the standard 100-share multiplier.

If C_net ≥ |K_short − K_long|, the trade has no risk and guarantees profit at expiration. This situation virtually never occurs in liquid markets because it would represent a risk-free arbitrage. If your inputs produce this result, double-check the premium values. The calculator will flag this as a no-risk scenario.

No. The results represent theoretical values before transaction costs. A credit spread involves 4 legs at open and close (sell one, buy one to open; buy one, sell one to close). Even at $0.65 per contract, that is $2.60 round trip per spread. On a 1-contract spread collecting $50, commissions consume 5.2% of max profit. Factor this into your true return on risk.

Credit spreads carry negative vega. A drop in implied volatility reduces the value of both legs, but the short leg (closer to the money) loses value faster than the long leg. This accelerates profit. Conversely, an IV spike inflates the spread's market value, creating an unrealized loss even if the underlying price hasn't moved adversely. Selling credit spreads in high-IV environments (e.g., before earnings) exploits the subsequent volatility crush.

Many traders target a risk-to-reward ratio (R:R) of 3:1 or lower, meaning risking no more than $3 to make $1. This corresponds to a return on risk of about 33%. Ratios above 5:1 indicate that the credit received is too small relative to the capital at risk. Such trades require very high win rates (above 83%) to be profitable over time.

No. A debit spread (bull call or bear put) involves paying a net premium, which reverses the profit/loss logic. The max profit for a debit spread is strike width minus net debit, while max loss is the net debit paid. The breakeven formulas also differ. Using this credit spread calculator for debit spreads will produce incorrect results.