Stable Numbers
ISA Transfer Benefit Calculator
Should you transfer from a Cash ISA to a Stocks & Shares ISA? Model both paths with fees, growth and contribution timing. See final balances, fees paid, a real-terms view and the break-even month where investing first pulls ahead.
Used to label the schedule months.
Cash ISA assumptions
Paid gross and compounded monthly for modelling.
Stocks & Shares ISA assumptions
Used to show real-terms balances.
Assumptions: monthly compounding for both paths. For S&S ISA, growth is gross; platform and fund fees are applied as a percentage each month, plus any fixed monthly fee. Contribution timing controls whether the monthly amount participates in growth for the full month. Markets can fall as well as rise. Treat growth as an assumption, not a promise.
Show monthly schedule
| # | Date | Cash start | Cash interest | Cash end | S&S start | Contrib | Growth | Fees % | Fixed fee | S&S end |
|---|---|---|---|---|---|---|---|---|---|---|
Real-terms values are shown in the summary. Schedule figures are nominal.
About this calculator
A Cash ISA offers a known interest rate and capital stability. A Stocks & Shares ISA adds market risk but can deliver higher long-run returns. This page compares both paths on equal footing. It separates S&S growth from fees so you can see what you are paying the platform and funds. It also accounts for contribution timing, which matters over long horizons because money added at the start of the month enjoys extra compounding.
Results show nominal balances as well as a real-terms view using your inflation input. The break-even month tells you when, under your assumptions, the investing route first overtakes the cash route. Remember that markets are volatile and can fall, sometimes sharply. Treat the growth rate as a planning assumption rather than a promise, and keep an emergency buffer in cash.
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