Should I invest a lump sum all at once?

Statistically, lump sum investing outperforms drip-feeding about two-thirds of the time because markets tend to rise. However, if investing a lump sum all at once feels too risky, investing it over 3–6 months is a reasonable compromise.

What return rate should I use for investments?

For a diversified global equity portfolio, 7% is a reasonable long-term assumption before inflation (approximately 4.5% real return). For more conservative portfolios or shorter time horizons, 4–5% may be more appropriate.

How do I minimise investment fees?

Use low-cost index funds (0.1–0.2% per year) on platforms with competitive pricing. For smaller portfolios, percentage-based fees are cheaper. For larger portfolios (£50k+), flat-fee platforms often save money.

How often should interest compound?

More frequent compounding (monthly or daily vs yearly) gives slightly better results, but the difference is usually small. Most savings accounts compound daily, while investments like index funds compound based on market returns.

Should I account for inflation?

Yes. Inflation erodes purchasing power over time. Use the Advanced Settings to add an inflation rate (2–3% is typical for the UK) to see your results in today's money. This gives a more realistic picture of future wealth.

What's the best strategy for compound growth?

Start early, contribute consistently, and let time do the work. Even small amounts grow significantly over decades. Increasing your contributions by a small percentage each year (use Advanced Settings) can dramatically boost your final balance.

CompoundWise

Turn £300/month into £196,665

Free UK calculator · No signup · Based on ISA investing

By CompoundWise Team·Updated April 2026

Starting amount

£0£20k£200k

Monthly contribution

£0£1k£5k

Expected annual return

Time horizon

yrs

Invest £300/month for 20 years at 7%

£114,665

earned in interest alone

That's more than you put in, your money earns money

Total value

£196,665

You put in

£82,000

Your money58% from compounding

To reach £196,665, most UK investors use a Stocks & Shares ISA

Most UK beginners start here

Open a free Stocks & Shares ISA

Trading 212 · No fees · Start from £1 · FCA regulated

Start your £300/month plan →

Open an account in 5 minutes · No minimum deposit

Capital at risk · Affiliate link · Not financial advice

Compare other platforms ↓

Keeping this in a savings account? You'd have ~£64,454 less

Compared to investing at 7% vs a 4% cash savings account

Growth Over Time

Recommended for your plan

Affiliate

Trading 212

Popular

No commission · Start from £1 · FCA regulated

No commission on stocks1M+ UK usersFree ISA included

Commission-free stocks & shares ISA. Clean app, no hidden charges, perfect for g...

Start with Trading 212 →

Capital at risk. These are informational suggestions, not financial advice.

Quick Scenarios

Your Personalised Insights

Year 16: your interest overtakes your contributions. From here, compounding does the heavy lifting.
Your money earns ~£16/day in interest. That's £114,665 earned while you sleep.
Saving just £50 more per month would add £26,047 to your final balance. That's £12,000 invested for £26,047 extra.
5 more years would add £103,611, nearly 53% more, showing how powerful time is.
Starting 5 years earlier would add £73,087 to your final balance. Every year you wait costs real money.Start investing now →
Consistency beats timing, investing £300/month for 20 years matters more than picking the perfect moment to start.
At your current plan, you reach £100k in 13 years. That's a real milestone, and it compounds from there.Start building towards it →

Best for beginnersAffiliate

Trading 212

Start from £1 · No commission · Popular with UK investors

Open free account →

Try These Scenarios

Invest £10,000 Lump Sum: Compound Interest CalculatorCalculate how a £10,000 lump sum investment grows over time. See projected returns at different rates with visual charts.Invest £50,000 Lump Sum: Wealth Growth CalculatorSee how a £50,000 lump sum grows with compound interest. Calculate projections with or without additional monthly contributions.How to Save £100,000: Compound Interest PlanFind out how much you need to save monthly to reach £100,000. Use compound interest to get there faster than you think.

Explore All Scenarios

Browse pre-built calculators by category.

What If You Invest £50 Per Month?See how even £50 per month compounds into real wealth over time. Free calculator with visual charts and year-by-year breakdown.What If You Invest £100 Per Month?See how investing £100 per month grows over time with compound interest. Calculate your projected returns with our free tool.Invest £200 Per Month: Compound Growth ProjectionCalculate how £200 monthly contributions grow with compound interest over 10, 20, or 30 years. Free visual calculator.Invest £300 Per Month: How Much Will It Grow?See how £300 monthly investments compound over 10, 20, or 30 years. Visual calculator with insights and year-by-year projections.Invest £500 Per Month: Long-Term Growth CalculatorSee how £500 monthly investments compound over time. Visualise your potential returns with charts and year-by-year breakdown.Invest £750 Per Month: Wealth Projection CalculatorCalculate how £750 per month compounds over time. See projected balances, interest earned, and milestone years.Invest £1,000 Per Month: Wealth Building CalculatorCalculate how investing £1,000 per month compounds over time. See projected balances, interest earned, and growth charts.Invest £1,500 Per Month: High-Earner Growth CalculatorSee how investing £1,500 monthly builds wealth over time. Projections for 10, 20, and 30-year horizons with compound interest.Invest £2,000 Per Month: Accelerated Wealth CalculatorCalculate how £2,000 monthly investments compound into serious wealth. See projections with charts, milestones, and breakdowns.

By the CompoundWise Team · Updated April 2026

UK-based financial education · Not financial advice

Lump sum vs regular investing

Both strategies work, and combining them is often most effective. A £10,000 lump sum at 7% grows to £38,700 over 20 years on its own. Adding £300/month on top grows the total to roughly £195,000. The lump sum benefits from maximum time in the market, while monthly contributions build the habit of consistent investing and benefit from pound-cost averaging during volatile periods.

Realistic return expectations for UK investors

UK investors in a globally diversified equity index fund have historically earned 7–10% per year before inflation. More conservative portfolios mixing bonds and equities might return 4–6%. Cash savings accounts offer 4–5% in the current environment but historically trail inflation over long periods. Use the rate slider to model different asset allocations.

The impact of investment fees on compound growth

Investment fees compound against you just as returns compound for you. A fund charging 1.5% per year vs 0.2% per year creates a massive gap over decades. On a £300/month investment over 20 years at 7% gross, the difference between 0.2% and 1.5% in fees is approximately £28,000 in lost growth. This is why low-cost index funds and fee-conscious platforms matter.

Frequently asked questions

Get weekly investing tips & calculator updates

Free, no spam. Unsubscribe anytime.