Free money tools
Change a number.
Understand the effect.
Simple, transparent calculators. All rates are assumptions you choose, not live quotes or return forecasts.
Use these tools as experiments.
- Start with the example and read what each output measures.
- Change one assumption at a time so the cause of the change is clear.
- Run a less favourable case and note which costs or uncertainties the tool omits.
These are educational scenarios. They do not assess affordability, recommend an investment or predict a market outcome.
01 / Compounding
What could regular
saving add up to?
Separate money you put in from modelled growth. Then compare the ending balance with what it could buy in today's money.
Illustrative ending balance
—- Money you paid in
- —
- Modelled growth / loss
- —
- Ending balance in today's money
- —
Annual ending balances. Each bar uses the same nominal scale.
How to read the result
Paid in is your starting balance plus contributions. Growth / loss is the nominal balance less that amount. Today’s money adjusts the final balance for the assumed price level; it is not the cash a bank would pay you.
Try 0% growth to isolate saving effort. Then change inflation while holding growth fixed: nominal wealth stays the same, but its modelled buying power changes. Use the CSV to inspect every year.
Assumptions and calculation method
The annual growth assumption is an effective rate. The monthly rate is (1 + annual rate)1/12 − 1. Contributions arrive at the end of each month and stay fixed in nominal pounds. Growth is applied monthly before each contribution. Inflation-adjusted ending value = nominal ending value / (1 + inflation)years.
No fees, tax, withdrawals or variable returns are included. Negative assumed growth is supported, but actual investment paths can be volatile and returns are not guaranteed. The inflation-adjusted amount describes the ending balance; it is not a calculation of an inflation-adjusted investment gain on all your contributions.
02 / Purchasing power
The number stays the same.
What could it buy?
Compare a fixed cash balance with the future cost of the same basket of goods and services.
Future spending power of unchanged cash, in today's pounds
—- Future cost of today's basket
- —
- Change in purchasing power
- —
Assumes a constant price-growth rate and cash earning no interest. Your personal spending mix may differ from an inflation index.
What the two amounts mean
Future basket cost asks how much money you would need later to buy today’s basket. Purchasing power asks what unchanged cash could buy, expressed in today’s pounds. They are different questions, not two competing forecasts.
Positive inflation makes the basket cost rise and unchanged cash’s purchasing power fall. Negative inflation reverses those directions. To model money earning a return, use the savings tool above.
Show the formulas
Future basket cost = today's amount × (1 + inflation)years. Purchasing power of unchanged cash = today's amount / (1 + inflation)years. The percentage change compares that purchasing power with today's amount. At a zero starting amount, the percentage change is undefined.
Apply the same curiosity to a business
What's behind
a valuation?
Change growth, margins and the discount rate in a fictional company case.
Sources & scope
Educational background: Investor.gov on compounding and the Bank of England on inflation. Reviewed 14 October 2026. Calculations are original implementations of the formulas shown. No inputs are sent to a calculation server.