Core-satellite: a simple way to build an ETF portfolio
Core-satellite is one broad, cheap fund at the centre — the ‘core’ — with a few small extras, the ‘satellites’, orbiting around it.
The big idea
Picture a wheel. In the middle sits your core — a broad, low-cost fund that does the heavy lifting. Around the edge sit a few small satellites — specific bets you find interesting. Most of the money stays in the calm, spread-out core; the satellites are the seasoning, not the meal. It’s a way to be sensible and scratch the itch to back a particular idea, without betting the house on it.
Building the core
The core is usually a broad global or regional stock ETF with a low yearly fee (the The yearly running cost of the fund, shown as a % of your money. Lower is cheaper. More → ). Its job is boring on purpose: hold a lot of companies, cheaply, for the long run. Because it’s doing most of the work, many people put the majority of their money here and add to it steadily — the part of the portfolio they mostly leave alone.
Choosing satellites (and keeping them small)
A satellite might be a single The kind of business a holding is in — for example technology, healthcare or finance. More → like technology, one The part of the world the fund invests in — for example world, US, Europe or emerging markets. More → , or a theme you believe in. The discipline is in the size: satellites are kept small on purpose, so that if one has a rough year it can’t sink the whole portfolio. If a ‘small’ bet grows into most of your money, it isn’t a satellite any more — it’s become the core, and the spread you started with is gone.
Why that discipline needs revisiting, not just setting
The size discipline in the last section isn’t a one-off decision — a core-satellite mix drifts on its own, the same way any portfolio does. A satellite that has a strong run can quietly grow well past the small size you started it at, without you doing anything at all. Left alone, ‘a small bet’ can drift into a large one exactly the way the last section warned against.
The fix is the same habit any portfolio needs: periodically trim back whatever’s grown into an oversized slice and top up the rest — rebalancing, just applied to the core/satellite frame instead of a stocks/bonds one. Checking once a year is plenty; there is no need to watch it daily.
It’s a shape, not a recommendation
Core-satellite is a useful shape for thinking about a portfolio — it is not an instruction to buy anything, and plenty of people happily skip the satellites entirely and hold just the core. We explain the structure so you can decide whether it fits how you want to invest. Which funds go in which slot is always your call.