Stop saving and start investing! How the FTSE 100 could turn £100 per week into a £1m ISA

I think the FTSE 100 (INDEXFTSE:UKX) offers strong long-term growth potential.

The content of this article was relevant at the time of publishing. Circumstances change continuously and caution should therefore be exercised when relying upon any content contained within this article.

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More.

Investing £100 per week and ending up with a seven-figure portfolio may sound like a pipe dream to most people. However, it could be a much more attainable goal than it first seems due to the long-term growth potential of the FTSE 100.

By investing in a range of large-cap shares, holding them over the long run and reinvesting your dividends, you could end up with a £1m+ portfolio. By contrast, investing in a Cash ISA or savings account may mean that you experience disappointing returns that fail to improve your long-term financial situation.

FTSE 100 potential

The FTSE 100’s total annual returns since its inception 36 years ago have been around 9%. Assuming a similar rate of growth in future, a £100 investment in the index could be worth over £1m over a 34-year period. This assumes that dividends are reinvested, and that no capital is withdrawn from your portfolio.

With the FTSE 100 currently appearing to offer good value for money, its future returns could prove to be relatively impressive. For example, it has a dividend yield of 4.4%, which is above its long-term average, while major sectors such as resources, energy and financial services appear to offer many stocks that trade on low ratings compared to their historic averages. Over the long run, those valuations may revert towards their averages, which may lead to higher returns for investors in the FTSE 100.

Cash prospects

While the FTSE 100 could catalyse your portfolio’s performance, holding cash or investing in a Cash ISA may not. At the present time, savers may struggle to obtain an income return above 1.5%. Assuming such a rate of return over the same 34-year period discussed above, paying £100 per week into a savings account would lead to a total balance of £228,000.

Clearly, there is scope for interest rates to rise over the coming decades. But history shows that cash returns have lagged the stock market’s returns, due to the lower risk of cash, which may mean that a higher regular investment than £100 per week is required to generate a £1m+ portfolio.

Risk/reward

While the FTSE 100 is a riskier place to invest compared to cash, investors with a long-term outlook are likely to have sufficient time to enable their short-term paper losses to recover. This could mean that, while holding a modest amount of cash for emergencies is a sound move, focusing your capital on the FTSE 100 is a better idea when it comes to improving your long-term financial situation.

Of course, buying high-quality shares while they trade at low prices could enable you to beat the FTSE 100 and generate even higher returns. This could shorten the amount of time it takes to produce a £1m+ portfolio, and may lead to greater financial freedom in older age.  

Peter Stephens has no position in any of the shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

More on Investing Articles

A young woman sitting on a couch looking at a book in a quiet library space.
Investing Articles

How are Lloyds shares looking in March 2026?

Lloyds shares have taken a tumble in the last month. What has happened? And could this be a golden opportunity…

Read more »

piggy bank, searching with binoculars
Investing Articles

Are Barclays shares really 50% cheaper than HSBC right now?

Barclays shares are trading at a price-to-book ratio half that of rivals like HSBC. Ken Hall looks at what the…

Read more »

Middle aged businesswoman using laptop while working from home
Investing Articles

Is Legal & General a top bargain after its 8% share price drop?

Looking for brilliant dividend shares to buy on the cheap? Royston Wild takes a look at Legal & General following…

Read more »

Silhouette of a bull standing on top of a landscape with the sun setting behind it
Investing Articles

Up 19% in a day, is there more to come from the surging Diploma share price?

Diploma’s share price is storming higher. But does the stock offer safety in an uncertain market, or is buying at…

Read more »

Portrait Of Senior Couple Climbing Hill On Hike Through Countryside In Lake District UK Together
Investing Articles

How much do you need in a Stocks and Shares ISA to target £2,000 a month of passive income?

With a bit of maths, our writer illustrates how an investor could shrink their initial ISA investment while supersizing dividend…

Read more »

Number three written on white chat bubble on blue background
Investing Articles

The FTSE 100’s full of value shares at the moment. Here are 3 to consider

Recent events have taken their toll on the share prices of some of the UK’s biggest companies. But it also…

Read more »

Investing Articles

Should I buy beaten-down UK growth stocks today or conserve my cash for even bigger bargains?

Harvey Jones says the FTSE 100 is packed with cut-price growth stocks after recent volatility. Should investors buy now or…

Read more »

Number 5 foil balloon and gold confetti on black.
Investing Articles

£5,000 invested in Fresnillo shares 5 weeks ago is now worth…

Fresnillo shares have pulled back sharply from recent highs in the FTSE 100. Is this a chance to consider buying…

Read more »