how to size an options position

In short

I once watched a neighbor spend an entire evening picking the perfect option, then bet far more than he could stand to lose on it. If you have ever done something close to that, you are in good company. The choosing is the fun part, and the sizing is the part that keeps you in the game. Start by deciding the most dollars you can lose on one trade without losing sleep. For a long option, that figure is the premium, which is the price you pay up front. Divide your loss limit by the cost of one contract to see how many contracts fit. Keep each trade small enough that a bad streak is an annoyance, not a disaster.

The whole of it

What it is

A friend of mine once told me that sizing a trade is like choosing how much salt to put in the soup. Too little and you taste nothing. Too much and you cannot eat it. Position sizing means deciding how many option contracts to trade, given how much money you can afford to put at risk.

One standard equity option contract usually covers 100 shares of the underlying stock. The Options Clearing Corporation, which stands behind listed options in the United States, publishes the contract terms. So when a quote says $2.50, the contract costs $2.50 times 100 shares, which is $250 before any commission. Many people miss that multiplier at first, and it has surprised better folks than me.

How it works

If you are buying a call or a put, the most you can lose is what you paid. That cap is a comfort, but it is not an excuse to go big. A hundred small losses add up just as fast as one large one. So the sizing question is how much of your account you are willing to see go to zero on a single idea.

Start with your account value. Pick a risk percentage that feels calm to you. Multiply the two, and you have your dollar loss limit for the trade. Then divide that limit by the cost of one contract. Round down, never up. The answer is the number of contracts that fit your plan.

Selling options works differently, and it asks for more care. A seller takes in a premium, but the possible loss can be much larger than that premium, and for an uncovered call it has no fixed ceiling. Brokers set margin requirements for these trades, which is money held back as a safety cushion. Those requirements follow rules from FINRA, the Financial Industry Regulatory Authority, and from the broker itself. For a seller, size the trade by the worst loss you can picture, not by the premium collected. That worst case is the number that matters.

Before anyone trades options at all, the broker must approve the account for a certain level. The Options Clearing Corporation publishes a booklet called Characteristics and Risks of Standardized Options, and brokers hand it to new options customers. It is worth an afternoon of your time.

The numbers, and where to find yours

Three numbers drive the whole thing. The first is your account value, which your broker statement shows. The second is your risk percentage, and that one comes from you, not from any rule. The third is the price of one contract, which you find on the option chain in your broker platform, multiplied by 100.

Some limits are set by law or by the exchanges, and those change over time. Position limits cap how many contracts one holder may control on a given stock, and the exchanges publish them. The pattern day trader rule sets a minimum account balance for frequent short term trading. It comes from rules set by the SEC and the exchanges, and FINRA enforces it. The minimum is the current figure, which the official source publishes each year. The FINRA website lists the current figure.

For ordinary folks trading a few contracts, those limits will rarely bind. Your own loss limit will bind first, and that is just as it should be.

A worked example

Let me tell you about a woman named Dolores, who keeps her books in a green notebook and her coffee too hot. Dolores has a brokerage account worth $20,000. She has decided that one trade should never cost her more than 2 percent of the account.

Her loss limit is 2 percent of $20,000. That is 0.02 times $20,000, which comes to $400.

Dolores likes a call option on a stock she follows. The option chain quotes the premium at $2.50. One contract covers 100 shares, so one contract costs $2.50 times 100, which is $250.

Now she divides her loss limit by the cost of one contract. $400 divided by $250 is 1.6. She rounds down to 1 contract. Her risk is $250, which is 1.25 percent of her account, safely under her limit. Two contracts would cost $500 and break her rule, so she stays at one.

Say the trade goes against her and the option expires worthless. She loses the $250 she paid. Her account falls from $20,000 to $19,750, a drop of 1.25 percent. She grumbles, tops off her coffee, and carries on. Nothing is broken.

Now suppose Dolores had skipped the math and bought 8 contracts because the idea felt sure. That is 8 times $250, or $2,000, which is 10 percent of her account on a single guess. If that expired worthless, she would be down to $18,000 and likely feeling sick about it. Same idea, same stock, very different night.

Where it goes wrong

I have noticed that the usual trouble is not bad math but bad feelings. After a loss, a person wants to win it back fast, so the next trade gets bigger. That is how a small dent becomes a deep hole. Hold your rule steady, especially on the days it annoys you.

Another slip is forgetting the 100 share multiplier and thinking a $2.50 option costs $2.50. Check the full cost before you click. Commissions and fees add a little more, so build them into the number.

Some folks size by how sure they feel. Feeling sure is not evidence. The market has humbled plenty of confident people, and I count myself among those who have learned it the slow way.

Sellers face a sharper edge. Selling an uncovered option can produce losses far above the premium received, and a broker can demand more money fast if the trade moves the wrong way. If the broker issues a margin call, the borrower has to add funds or the broker may close the position. Know that before you size anything.

Last, remember that options lose value as time passes. A contract can expire worthless even when the stock barely moves against you. Size for that outcome, because it is a common one.

Questions to answer before you leave this page

What is the most you could lose on a single trade and still sleep well, and what percent of your account does that amount represent? Have you multiplied the quoted premium by 100 to find the true cost of one contract, and added the commission? Does rounding down leave you with at least one contract, and if it does not, is the trade simply too big for your account right now? If you are thinking of selling options, have you read the Characteristics and Risks of Standardized Options booklet from the Options Clearing Corporation, and do you know what your broker will require in margin? Which number on your broker statement tells you your account value today, and have you written your risk percentage somewhere you will see it before the next trade?