A tree planted today gives no shade today. For years, it can look like nothing is happening above the ground, while the roots quietly do the real work below it. Then, one year, the tree is suddenly tall enough to matter, and the shade arrives all at once. A £100,000 pot works the same way.

Someone's sitting in the shade today because someone planted a tree a long time ago.Warren Buffett

Every investment pot is made of two different things. One part is money that was actually put in, pound by pound, over the years. The other part is money the pot earned on its own, growth building on growth. Early on, the money put in does almost all of the work. The growth barely shows.

Take a simple example: £200 invested every month, growing at a steady 7% a year. As the pot grows, the balance between these two parts shifts, quietly, year after year.

Money Put In vs Money the Pot Earned
£200 a month, growing at a steady 7% a year
£35k Year 10 £104k Year 20 £244k Year 30 £525k Year 40 Money earned overtakes money put in, around here
Money put in
Money the pot earned
By year 20, £56,000 of the £104,000 pot is money the pot earned on its own, more than the £48,000 that was actually paid in. The exact pot size where this happens depends entirely on how much is contributed and what return is earned. A smaller monthly amount or a lower return moves this crossover to a very different size of pot, not necessarily anywhere near £100,000.

This is why £100,000 gets treated as a milestone worth naming. Not because the number itself is special, but because it tends to land close to the point where growth stops being the smaller part of the story.

In the same example, the acceleration shows up in time, too, not just in the split between contributions and growth.

The Next £100,000 Arrives Faster
Same £200 a month, growing at a steady 7% a year
~20 years
To reach the first £100,000
→
~8 years
To go from £100,000 to £200,000
The second £100,000 arrives in less than half the time of the first, in this example, because it is compounding on a much bigger base. This is specific to this contribution amount and this return. A different monthly amount or a different return changes both numbers, and markets do not actually deliver a steady 7% every single year the way this example assumes.
The first $100,000 is a b**, but you gotta do it. I don't care what you have to do. If it means walking everywhere and not eating anything that wasn't purchased with a coupon, find a way to get your hands on $100,000. After that, you can ease off the gas a little bit.Charlie Munger, widely cited from talks and interviews

One way to see the significance is to compare what a single good year returns with what a year of steady contributions adds, at different pot sizes.

What a 10% Year Is Actually Worth
A 10% return on three different pot sizes, measured against the £200-a-month contribution used throughout this example
£1,000 pot
£100
about half a month's contribution
£20,000 pot
£2,000
about ten months of contributions
£100,000 pot
£10,000
over four years of contributions
At £1,000, a 10% return is £100, less than a single month's £200 contribution. At £20,000, it is £2,000, close to a year of contributions. At £100,000, it is £10,000, over four years of contributions in a single year. A real saver at that size has usually raised their contributions too, so the true gap is often smaller than this. The mechanism still holds regardless: past a certain pot size, growth outweighs a year of adding money.

Before this point, a pot can feel like it barely moves, no matter how consistent the saving is. After it, the same consistent saving can look like it is accelerating on its own, because more of the growth is coming from money that was already there, not money being added that month.

01

A pot's size is made of two different things: what was put in, and what it earned on its own.

Only one of those two keeps compounding without any further input at all.

02

Early on, money put in does most of the work. Past roughly £100,000, growth typically becomes the bigger driver of the pot.

The money still being added matters less and less to the outcome, even though it has not stopped mattering.

03

£100,000 is not a magic number. It is simply, for a realistic saver, roughly where this switch tends to land.

The real number for any given saver depends entirely on how much is being contributed and what return is being earned.

None of this says £100,000 is a target worth reaching, or how long it should take any particular saver to get there. It shows why the number gets talked about the way it does: not because of anything special about it, but because of what usually happens to the balance between contributions and growth somewhere around a pot that size.