Volatility targeting: sizing investments by risk, not by dollars

Volatility targeting is a way of deciding how much money goes into each investment based on how much it swings, not on how many dollars it holds. Each holding is sized by its risk, and when markets get wilder, positions shrink. When markets calm down, they grow again. The result is a portfolio whose risk stays close to the level the investor chose, instead of drifting with the market's mood.

Why equal dollars do not mean equal risk

Most investors think about their portfolio in dollars: $10,000 here, $5,000 there. But a dollar in one asset can carry far more risk than a dollar in another. The lesson measures annualised volatility from weekly total returns, from the start of each fund to June 2026 (past performance is not a guide to the future):

Bitcoin's 68% is four times the S&P 500's 17%. So one dollar in Bitcoin carries about four times the risk of one dollar in the S&P 500.

Now imagine putting 25% of your money into each of these four assets. On paper that looks balanced. In practice, Bitcoin would dominate. As a rough calculation that ignores how the assets move together, Bitcoin's 68% makes up about 59% of the combined volatility of the four (68 out of 14 + 17 + 17 + 68 = 116). A quarter of the money, more than half of the risk.

Sizing by risk: how $100 would be split

The alternative is to let each asset contribute about the same amount of risk. The standard way to do this is to weight each asset by the inverse of its volatility: the more it swings, the less money it gets. This idea is often called risk budgeting.

Using the volatility figures above, an illustrative equal-risk split of every $100 looks like this:

• $36 in long-term Treasuries
• $29 in the S&P 500
• $28 in gold
• $7 in Bitcoin

Bitcoin still has a place, but at $7 instead of $25 it can no longer decide the fate of the whole portfolio. Each of the four parts can now hurt the portfolio by roughly the same amount. This is diversification measured in risk, not in dollars.

How volatility targeting adds a moving target

Equal-risk weights are a snapshot. Volatility targeting takes the idea one step further, because risk is not constant. In calm markets volatility is low. In a crisis it can double or triple within a few weeks.

A portfolio with a volatility target works roughly like this:

1. It sets a target level of risk. 2. It measures its current volatility at regular intervals. 3. When measured risk rises above the target, it reduces its positions. 4. When markets calm down, it increases them again, up to its normal size.

Some versions cap exposure at 100% of the capital, so they never borrow to add exposure in calm periods. Others use leverage. The difference matters, because borrowing adds its own risks.

The target itself is a personal choice. A lower risk target generally means smaller falls and lower expected returns. A higher target means the opposite. Volatility targeting does not remove that trade-off. It keeps the risk you carry closer to the risk you picked.

Why it helps: volatility clusters

The reason this approach works at all is a well-known feature of markets: volatility clusters.

• Wild weeks tend to follow wild weeks.
• A crash comes with exploding volatility.
• Calm periods tend to last.

If risk were random from week to week, measuring it would tell you nothing about the next week. Because it clusters, a jump in volatility is a useful warning that the coming weeks may also be rough. Cutting size when risk jumps means a portfolio takes smaller hits during the most dangerous phases. When calm returns, size comes back.

The practical effects:

• Smaller falls in wild markets, because less money is exposed when swings are largest.
• A steadier ride, which makes it easier to stay invested.
• Risk close to what you chose, rather than risk set by whatever the market is doing that month.

One limitation is worth keeping in mind. Volatility is measured from recent data, so a sudden shock out of a calm market can hit before the measured risk catches up. Volatility targeting softens the worst phases. It does not prevent losses.

Putting the pieces of diversification together

Risk-based sizing is the final piece of a broader view of asset allocation:

• Combine assets with genuinely different return engines.
• Check how they actually move together, because correlations change.
• Fixed mixes help, but they cannot react when diversifiers fail.
• Size every part by its risk, so no single holding dominates.

What to do with this

• List your holdings with their volatility. Most fund fact sheets and financial data sites show annualised volatility or standard deviation.
• Find your biggest risk, not your biggest position. Multiply each holding's weight by its volatility. The largest result is often a small position in a high-swing asset.
• Compare with an inverse-volatility split. Divide 1 by each asset's volatility and scale the results to 100%. See how far your current weights are from equal risk.
• Decide on your own risk level. Ask how large a fall you could live with, and consider whether your current mix matches it in calm and in wild markets.

This article is based on Lesson 5.4 of our course Mastering Investments, where Module 1 is free.

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