Interest rates are set by a committee that meets, announces one number, and within weeks changes your mortgage quote, your savings account and eventually the price of things in shops have all shifted. The chain connecting those events is not obvious, and understanding it explains a great deal of economic news that otherwise reads as noise.
Written September 2026. The mechanism is broadly the same across major central banks, though names and details differ.
The one rate a central bank actually controls
A central bank does not set mortgage rates or savings rates. It sets the rate at which commercial banks can borrow from, and deposit with, the central bank itself. In the UK this is Bank Rate; in the US, the federal funds target; in the euro area, the ECB deposit rate.
That single rate is the foundation everything else is priced from. If a bank can earn a dependable return by leaving money at the central bank, it will not lend to you for less, plus a margin for its costs and the risk you do not repay. Move the foundation and the whole structure moves.
Who decides, and on what basis
Decisions are made by a committee on a published schedule, usually eight times a year. Most major central banks have a mandate centred on price stability, commonly an inflation target of around two percent, sometimes alongside a secondary objective such as employment.
The committee is not steering today’s inflation, which is already determined. Rate changes take roughly eighteen months to have their full effect, so the committee is forecasting where inflation will be well ahead and acting on that. This is why decisions often look wrong at the time and sensible in hindsight, or the reverse.
Why it is a blunt instrument
There is one lever and many problems. The same rate rise that cools an overheating housing market also raises borrowing costs for a manufacturer planning an expansion, and squeezes a household that borrowed nothing recently but holds a variable rate mortgage. Central banks cannot target the part of the economy causing the trouble, which is the fundamental limitation of the tool.
How interest rates reach your money
- Mortgages. Variable and tracker rates move almost immediately. Fixed rates move at renewal, so the effect arrives in waves as households come off old deals, sometimes years later.
- Savings. Rise more slowly than borrowing costs, and by less, which is a persistent and widely noticed asymmetry.
- Credit cards and overdrafts. Loosely connected. These are priced mostly on default risk, so they stay high regardless.
- Business investment. Projects that made sense at low rates stop making sense at higher ones, which slows hiring and expansion.
- Currency. Higher rates tend to attract foreign capital and strengthen the currency, which makes imports cheaper and exports harder.
- Prices in shops. The end of the chain and the slowest link. Demand cools, firms find it harder to raise prices, and inflation eases.
What actually moves a decision
If you want to anticipate rate decisions rather than react to them, the committee watches a short list: inflation and particularly core inflation with food and energy stripped out, wage growth, unemployment, and measures of expectation. That last one matters more than people expect. If businesses and households come to expect high inflation, they price and bargain accordingly, and the expectation becomes self-fulfilling. A great deal of central bank communication exists purely to manage that.
What this means for your decisions
Two practical implications follow. First, fixing or not fixing a mortgage is a question about certainty rather than about beating the market. Rate expectations are already priced into fixed deals, so a fix buys predictability, not a guaranteed saving.
Second, savings rates need shopping around when rates rise, precisely because banks pass increases on slowly and incompletely. The gap between the best available rate and the one on an account you opened years ago is usually far larger than any recent change in interest rates.
For the government borrowing side of the same picture, our explainer on how government debt works covers why rates matter to public finances, and how tariffs affect prices covers a different route to the same shop shelf.
Why the same decision helps some households and hurts others
Interest rates redistribute as well as restrain, and the split is worth seeing clearly because it explains why rate news lands so differently depending on who you ask.
- Borrowers on variable deals feel a rise immediately and in full. Households with large mortgages relative to income are the most exposed group in any economy.
- Savers with substantial deposits benefit, though less and more slowly than the headline suggests.
- Households with fixed mortgages feel nothing until renewal, and then feel several years of change at once.
- Renters are affected indirectly, since landlord costs and housing supply both respond to rates, usually with a lag.
- People with no debt and no savings experience rate changes mainly through prices and job security, which is the slowest and least visible channel.
This is why a single rate decision produces genuinely contradictory reporting on the same day. Both accounts can be accurate about different households.
What a central bank cannot fix
Interest rates work by cooling demand. That makes them effective against inflation caused by an economy running hot, and close to useless against inflation caused by a supply shock such as a war, a drought or a broken supply chain. Raising rates does not produce more gas or more wheat. Committees say this openly, and it is worth remembering whenever a rate decision is criticised for failing to solve a problem it was never able to reach.
Common questions
Who sets interest rates? A central bank committee, on a published schedule, usually about eight times a year. They set the rate banks pay to borrow from the central bank, not the rates you are offered directly.
Why do savings rates rise more slowly than mortgage rates? Because banks are not obliged to pass increases on and compete less aggressively for deposits than for borrowers. It is why shopping around after a rate rise is usually worth more than the rise itself.
How long do rate changes take to work? Roughly eighteen months for the full effect, which is why committees act on forecasts rather than current inflation, and why decisions often look mistimed as they are made.
Should I fix my mortgage when rates change? Fixing buys certainty rather than a certain saving, since expectations are already priced into fixed deals. The right question is how much predictability is worth to your household budget.
Sources and further reading
Where the figures and rules above come from, so you can check them:
- How a central bank sets and explains its rate decisions: Bank of England
- Monetary policy transmission to the wider economy: European Central Bank
When you come to compare actual offers, the headline rate is only half the price. Our guide to APR vs interest rate covers where the rest of it hides.
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