Decision Tool

Invest vs Save — Which Wins?

Over the long run, investing beats saving — but with volatility. This calculator shows the mathematical gap at your horizon, plus two downside scenarios so you can see the trade-off clearly. Not a recommendation to invest if the horizon is wrong.

Pennywise Finance Editorial

Compares deterministic growth of saving (Cash ISA rate) vs investing (equity return assumption) plus two volatility scenarios: 10-year flat and -30% crash recovery.

Fact-checked
Reviewed September 2026
About our calculators

Runs entirely in your browser — your numbers are never sent to a server.

Your numbers

Monthly amount£

Expected cash rate%

Expected equity return%

Global equity long-run 6-8%.

Years

Result

Saving final (base case)—

Investing final (base case)—

Likely gap—

Bad investing scenario (first 10 years flat)—

The horizon decides the right answer

For money you need within 5 years: save. For money you don't need for 10+ years: usually invest. Between 5-10 years is personal preference around volatility tolerance.

Why 5-year rule matters

Historically, 5-year rolling returns on global equity can be negative. 10-year rolling returns have very rarely been negative. 20-year rolling returns essentially never have been. Longer horizon = volatility matters less relative to compounding.

The volatility scenarios

Base case: steady annual return at your chosen rate
Bad investing scenario: first 10 years return 0%, then recover — demonstrates sequence-of-returns risk

Real markets don't return constant rates. These scenarios make the risk visible, not just hidden in a smooth projection.

What this does NOT model

Specific fund/platform fees (use Investment Fee Calculator)
Dividend tax outside wrappers (use Dividend Calculator)
Inflation (figures are nominal)
Catastrophic market events

Frequently asked questions

Can equities really lose money over 10 years?

Yes, occasionally. 2000-2010 was close to flat for most equity indices. 1929-1945 was negative in real terms.

Should I invest my house deposit?

No, if the purchase is within 5 years. Volatility can take 2-3 years to recover and you cannot afford that delay.

What about global diversification?

All projections here assume broad diversification (global equity index, not single stocks). Single-stock risk is substantially higher.

Projections assume a fixed annual return — real markets do not return the same figure every year. Capital at risk. Past performance does not guarantee future results. General information only, not personalised financial advice.