How to hedge a portfolio with index futures (and how many contracts)

Hedging a portfolio with index futures is one of the few trades where the arithmetic matters more than the opinion. Get the contract count wrong and you are not hedged: you are speculating in the opposite direction while believing you are protected.

What does hedging a portfolio mean?

Opening a position that gains when the portfolio loses, to neutralise market risk without selling what you hold. You use it when you want to keep the positions — because you believe in them long term, because selling has a tax cost, or because they are illiquid — but you do not want to eat the drawdown.

With index futures it is cheap and fast: a single short order neutralises the part of your risk that comes from the whole market, which in a diversified equity portfolio is usually most of it.

How many contracts: the formula

Contracts = (portfolio value × beta) ÷ (index level × point value). Beta is how much your portfolio moves when the index moves 1%: a tech-heavy book with a beta of 1.3 falls 13% when the index falls 10%, and hedging it as if beta were 1 leaves it half covered.

The denominator is the notional value of ONE contract: the index level times what a point moves. With the S&P at 5,000, one ES ($50/point) covers $250,000 of exposure and one MES ($5/point) covers $25,000.

A worked example

A $180,000 US equity portfolio with a beta of 1.15 to the S&P 500, index at 5,000.

• Exposure to hedge: 180,000 × 1.15 = $207,000.
• One ES notional: 5,000 × 50 = $250,000. That is 0.83 contracts → round to 1 and you are 21% over-hedged, or to 0 and you have no hedge at all.
• One MES notional: 5,000 × 5 = $25,000. That is 8.28 contracts → 8 micros, a 3.4% miss.

That is the entire micros argument applied to hedging: the problem is not size, it is resolution. With full-size contracts a mid-sized portfolio's hedge can only be badly over or badly under.

What a hedge does NOT do

• It does not remove specific risk. Hedge with the S&P while holding biotech and you are still exposed to what happens to biotech. You only neutralise the market.
• It is not free just because you pay no premium. You give up the upside in the same proportion: fully hedged, a 10% rally gives you nothing.
• It does not maintain itself. If the portfolio rises the hedge falls short; if it drops you are over-hedged. And the contract expires, so it has to be rolled every quarter.
• It does not fix a badly built portfolio. Hedging is expensive in attention; if a position forces you to hedge permanently, the problem is the size of the position.

Full or partial

Nothing obliges you to hedge 100%. Hedging half the exposure halves the drawdown and keeps half the upside, and it is usually a saner decision than all-or-nothing — not least because timing the removal of a hedge is as hard as timing a full exit.

Common practice: write down a hedge ratio before you need it, and revisit it at the quarterly roll rather than improvising it on the day the market drops 3%.

Why index futures and not something else

Because they settle in cash. An index future cannot deliver anything to you: at expiry the difference is booked. Hedging with a physically delivered contract — crude, gold, Treasuries — adds the First Notice Day problem on top of the problem you already had, and a hedge that requires watching delivery dates has stopped being a simplification.

What this article cannot tell you: whether you should hedge. That depends on your horizon, your tax position and what it costs you to sleep. What is objective is the contract count — and if that number is wrong, the decision no longer matters.