How much can I make investing £100 a month?

At 8% average annual returns, investing £100/month for 10 years gives you roughly £18,400 (£12,000 invested + £6,400 growth). Over 20 years that becomes £58,900. Over 30 years: £149,000. The longer you invest, the more compound interest does the heavy lifting.

Is £100 a month enough to invest?

Absolutely. £100/month is a solid start. Many successful investors began with less. The key is consistency — investing every month matters more than the amount. Start with what you can afford and increase over time.

Where should a UK teenager invest £100 a month?

For UK teens, a Junior Stocks & Shares ISA is the best option. Choose a low-cost platform like Trading 212 or Vanguard, and invest in a global index fund like FTSE All-World (VWRL). This gives instant diversification across 3,700+ companies with fees under 0.25%.

How much is £100 a month invested for 3 years?

Investing £100/month for 3 years at 8% average returns gives you approximately £4,100 — that's £3,600 invested plus around £500 in growth. Not life-changing, but it builds the habit and knowledge that leads to bigger returns later.

Investing £100 a Month: What UK Teens Can Build Over Time

"£100 a month? That's barely anything."

That's what I thought too. Turns out I was dead wrong.

£100/month isn't going to make you rich overnight. But give it time, and compound interest does something genuinely mental. Let me show you the actual numbers.

The Raw Numbers: £100/Month at Different Timeframes

Assuming around 8% average annual return (roughly what global stock markets have done historically):

Timeframe	Total Put In	Final Value	Free Money (Growth)
3 years	£3,600	~£4,100	£500
5 years	£6,000	~£7,400	£1,400
10 years	£12,000	~£18,400	£6,400
20 years	£24,000	~£58,900	£34,900
30 years	£36,000	~£149,000	£113,000
40 years	£48,000	~£349,000	£301,000

Read that last row again. £48,000 invested. £301,000 in free growth. That's the power of starting at 15 instead of 25.

Why Starting at 15 Is Actually Broken

This is the bit that blew my mind.

🟢 Person A: Starts at 15

Invests £100/month for 10 years (ages 15-25), then stops completely.

Total invested: £12,000

Value at 45: ~£86,000

🟡 Person B: Starts at 25

Invests £100/month for 20 years (ages 25-45), never stops.

Total invested: £24,000

Value at 45: ~£58,900

Person A invested half the money, stopped 20 years earlier, and still has MORE.

That's not a typo. That's compound interest being absolutely unfair in the best way possible.

OK But Where Do I Actually Put £100/Month?

Right. Practical bit. Here's what I'd do (and basically what I am doing):

Open a Junior Stocks & Shares ISA

Tax-free growth until 18. Up to £9,000/year allowance. This is the obvious play for under-18s in the UK.

Pick a Low-Cost Platform

Trading 212 (zero commission), Vanguard (low fees), or InvestEngine (free for ETFs). Don't pay fees you don't need to.

Buy a Global Index Fund

Something like Vanguard FTSE All-World (VWRL) — 3,700+ companies in one fund. Instant diversification. Fees under 0.25%.

Set Up Auto-Invest

Most platforms let you auto-invest monthly. Set it and forget it. Remove the temptation to check every day.

Don't Touch It

Seriously. Markets dip. You'll see red months. The absolute worst thing you can do is panic sell. Just keep going.

What If I Can Only Afford £50? Or £25?

Still worth it. Here's £50/month for context:

Monthly	After 10 Years	After 20 Years	After 30 Years
£25/mo	£4,600	£14,700	£37,300
£50/mo	£9,200	£29,500	£74,500
£100/mo	£18,400	£58,900	£149,000
£250/mo	£46,000	£147,300	£372,500
£500/mo	£92,000	£294,500	£745,000

All figures assume 8% average annual return. Real returns will vary year to year.

Even £25/month gets you nearly £40k over 30 years. The amount matters less than the consistency.

The Cost of Waiting

Every year you delay costs you more than you think.

⏰ £100/month — the price of delay

Start at 15 → £349,000 by 55
Start at 18 → £272,000 by 55 (lost £77k)
Start at 25 → £149,000 by 55 (lost £200k)
Start at 30 → £98,000 by 55 (lost £251k)

Three years of waiting (15 → 18) costs you £77,000. That's the real price of "I'll start later."

What I'm Actually Doing

My situation is different. Dad puts in £500/month and I'm going high-risk with individual stocks because I need £60k in 3 years for uni. That's NOT the safe play.

If I was doing the sensible thing? I'd stick £100-250/month into VWRL inside a Junior ISA and not look at it for 10 years. Boring. But the numbers don't lie.

Read why index funds are the sensible path →

Try It Yourself

Don't take my word for it. Plug your own numbers into our Compound Interest Calculator and see what your £100 could become.

The Bottom Line

£100/month invested from age 15 can become £149,000 by 45 — with only £36,000 actually invested. The rest is compound interest doing its thing.

You don't need to be rich to start investing. You need to be consistent and early. And if you're reading this at 15, you've already got the biggest advantage: time.

Disclaimer: I'm 15. This isn't financial advice. These are projections based on historical averages — actual returns will vary. Markets go down as well as up. Do your own research and talk to your parents before investing.