What it means
Options traders bet on volatility indirectly, through option prices. A variance swap bets on it directly: pure exposure to how violently a market actually moves.
The contract is a forward on realised variance: at expiry, one side pays the realised variance of the underlying's returns over the period, the other pays the fixed strike agreed at inception, and the difference settles in cash. The strike is the market's forecast: it approximates the implied volatility squared, so buying a variance swap is betting that realised turbulence will exceed what the option market priced.
The contract's elegance is purity: unlike an option, whose volatility exposure leaks into direction and time decay, the variance swap isolates the volatility bet with no view on where the market ends up. Dealers love the structure because it is replicable: a strip of options across all strikes, weighted by one over strike squared, reproduces the payoff, which is how the desk hedges and how the strike is fair-valued.
Oxford's mathematical finance group, surveying the market's evolution, notes how 2008-9 disrupted single-name variance swaps so completely that the market never recovered, while index variance lived on. The contract's family is large: volatility swaps pay on the square root of variance, correlation swaps on co-movement, and the VIX itself is built from the same option-strip mathematics.
For a non-finance reader, a variance swap is a bet on how rough the sea will be next quarter, settled by measuring the waves, with no opinion about where any ship lands. The instrument's pricing connects deep ideas in derivatives theory.
The fair strike equals the expected variance under the risk-neutral measure, computable from option prices across strikes without any model of volatility dynamics. This model-free replication, worked out in the 1990s, is the same mathematics behind the VIX index.
In practice
Real-world examples.
Example
A fictional volatility fund sells index variance through a quiet summer and collects the gap between the priced and delivered calm. Each week the strike looks generous and the realised variance comes in low. An autumn shock then doubles realised volatility and the summer's premium is erased in a few weeks.
Example
A fictional pension scheme with a large equity portfolio buys variance on a regional index as protection. It pays the strike variance and expects to be repaid if markets turn violent. The position costs nothing if markets stay calm beyond the loss on the strike, and pays heavily in a crash.
Example
A fictional options desk sells a variance swap to a client and hedges it with a strip of options across all strikes, weighted by one over strike squared. The desk's profit is the bid-offer spread, not a view on volatility. It watches liquidity closely, because the hedge is hardest to adjust exactly when markets are moving fastest.
Formula
Calculation
Payoff at expiry = variance notional x (realised variance - strike variance), where realised variance is computed from the annualised sum of squared daily log returns over the period and the strike approximates implied variance from the option strip. Volatility swaps pay on realised volatility rather than its square, softening the tail.
Worked example: a buyer holds a variance swap with a variance notional of $1,000 per volatility point squared and a strike of 20 volatility points, so the strike variance is 20 x 20 = 400. If the market delivers 30 points of realised volatility, realised variance is 30 x 30 = 900, and the buyer receives $1,000 x (900 - 400) = $500,000. If instead realised volatility is only 15 points, realised variance is 225 and the buyer pays $1,000 x (225 - 400) = $175,000, which shows how the squared payoff rewards big volatility surprises far more than calm ones.Case study
Seen in the real world.
This case study is fictional and illustrative. A made-up volatility fund's PM spends the quiet summer selling index variance, collecting the gap between priced and delivered calm, and her risk officer spends the same summer asking what the position loses in a crash. The answer, modelled daily, is a number that keeps the position sized small: variance short positions lose quadratically when realised volatility spikes. The autumn delivers the exam: a policy shock doubles realised volatility in three weeks, the variance swaps settle at twice the strike, and the fund's quarter of careful premium collection evaporates in days. The post-mortem avoids the easy lesson: selling variance is not wrong, it is short an insurance product, and the fund's error was sizing the position by premium collected rather than by crash loss.
The rebuilt framework treats variance like the insurance it is: position limits keyed to the tail scenario, diversification across regional indexes whose crashes do not coincide, and a standing long position in far-dated variance that bleeds slowly but pays in the exact scenarios the short book fears. The PM's presentation at the next allocator conference draws the honest crowd: everyone in the room has collected premium in the same trade and paid for the same education. Her closing slide is the contract's one-line character reference: variance swaps are the purest volatility instrument ever traded, and purity cuts both ways. The rebuilt book's first full year validates the redesign: premium income halves, drawdown in the next volatility spike shrinks by two-thirds, and the allocator meetings stop featuring the crash question. Her year-end letter to investors quotes the risk officer's framing from the autumn that started it: the premium was never the product, the tail was the product, and we now charge for it properly.
Watch out
Common mistakes.
- Treating it like an option; variance swaps carry no delta hedge or strike selection, so their purity makes losses arrive faster than option sellers expect.
- Ignoring the squared payoff; losses grow with the square of the volatility surprise, so tail sizing, not premium, must set position limits.
- Assuming liquidity in stress; single-name variance markets proved in 2008 that these contracts can become untradeable exactly when they matter most.
Questions
People also ask.
What is a variance swap?
A derivative settling on the difference between an asset's realised variance over a period and a fixed strike agreed at inception.
Why trade it instead of options?
It gives pure volatility exposure without directional or time-decay contamination, replicable by dealers with a strip of options.
What are its risks?
Short positions lose quadratically when volatility spikes, and market liquidity can vanish in crises, as 2008 proved for single names.
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