Savings Account Interest Calculator

What savings account rates actually represent

Savings rates in 2024-2025 are at their highest in over 15 years — typically 4-5% on easy-access accounts. This reverses a decade where rates were 0.5-2%, during which "cash was trash" for most purposes. The current rates create real questions: should you hold more cash? For how long? Against what alternatives? This calculator projects savings growth; the commentary below is about what the numbers mean in a rate environment most current savers have never seen before.

The four savings account types

Easy-access: Current best rates 4.5-5%. Full instant access, variable rate can be cut at short notice. Best for emergency funds and short-term savings.

Notice accounts: Typically 30-180 days notice to withdraw. Rates slightly higher than easy-access (about +0.2-0.4%) to compensate for reduced flexibility.

Fixed-rate bonds: 1-5 year terms, rates locked for the term. Current 1-year typical 4.5-5%, 5-year 4.3-4.7%. Lower rates on longer terms because banks expect rates to fall. Early withdrawal usually penalized (loss of some interest, sometimes access disallowed).

Regular savers: Monthly deposit limits (typically 200-500), often 12-month terms. Top rates can exceed 7% but are limited in total amount. Niche product useful for specific goals.

Most households benefit from using easy-access for emergency fund, plus some fixed-rate bonds for longer-term cash reserves. Regular savers make sense for specific goals (house deposit, wedding). Notice accounts are usually not worth the complexity.

AER vs gross vs net

Savings rates are quoted as AER (Annual Equivalent Rate) — the rate accounting for compounding frequency, expressed as annual. This lets you compare accounts with different compounding periods fairly. A 4.9% AER compounded monthly matches a 4.97% AER compounded daily. AER is gross (before tax). Net rate after tax depends on your Personal Savings Allowance and marginal tax rate.

Personal Savings Allowance (PSA) for:

standard rate (under 50,270 income): 1,000 of interest per year tax-free.

Upper rate (50,270-125,140): a local tax-free.

top rate (above 125,140): a local tax-free.

At 4.5% AER, the 1,000 PSA covers about 22,200 of savings for standard-rate taxpayers. 500 PSA covers about 11,100 for higher-rate. Beyond that, interest is taxed at marginal rate.

The tax-advantaged account advantage at current rates

cash savings account currently offer nearly identical rates to standard savings accounts (around 4.5-4.9% for easy-access; 4.3-4.7% for fixed-rate). The advantage: all interest is tax-free, regardless of how much you have in the tax-advantaged account. For savers with substantial cash holdings (25,000+), the tax efficiency matters. For a upper-rate taxpayers with 50,000 in savings at 4.5%:

Standard account: 2,250 interest. PSA covers 500, 1,750 taxed at 40% = 700 tax. Net: 1,550.
cash savings account: 2,250 interest, no tax. Net: 2,250.

The 700 difference is meaningful. For anyone likely to exceed PSA thresholds (most upper-rate taxpayers with emergency funds or house deposit savings), cash savings account is structurally better than equivalent non-tax-advantaged accounts.

The compounding frequency that matters

Daily vs monthly vs annual compounding produces different final values, though the differences are smaller than marketing sometimes implies. 10,000 at 4.5% for 10 years:

Annual compounding: 15,530.

Monthly compounding: 15,660.

Daily compounding: 15,683.

Difference between monthly and daily: 23 over 10 years on 10,000. Negligible. The AER figure accounts for compounding automatically, so comparing AER-to-AER across accounts is the favoured option regardless of the marketing emphasis on "daily compounding".

The FSCS protection context

Savings accounts with FSCS-regulated banks are protected up to 85,000 per depositor per banking group. For larger savings, spreading across multiple banking groups matters. Several banks operate under shared FSCS cover (e.g., HSBC and First Direct share cover; Royal Bank of and NatWest share cover). Check the FSCS bank list if your savings exceed 85,000 in any single institution. Some newer challenger banks offer higher rates but operate under partial protection — verify coverage before transferring large amounts.

When cash beats investment

At current savings rates (4.5%+), cash genuinely competes against some investment alternatives:

vs cash savings account: Same rate, same tax treatment. tax-advantaged account wins on tax-efficiency once PSA is exceeded.
vs premium bonds: Average prize rate around 4.4%. Roughly equivalent returns, but variance; some winners, most receive less than rate implies. Tax-free like ISAs.
vs short-dated bonds (under 2 years): Gilt yields around 4.3-4.5%. Comparable to easy-access, with small premium for locking.
vs global equity (short horizons under 2 years): Cash at 4.5% with certainty vs equity with 7% expected return and 25% potential downside. For money needed within 2 years, cash wins risk-adjusted.
vs global equity (long horizons over 10 years): Equity historically returns 5-7% real vs cash 0-1% real. Equity wins comfortably on long horizons.

Matching holding period to vehicle matters — cash applies for 1-3 year horizons even at today's attractive rates; equities make more sense for 10+ year horizons even when cash rates are attractive in absolute terms.

Rate-chasing reality

Savings rates change. A 5% easy-access rate today could drop to 3% in 18 months if the the central bank cuts rates. Fixed-rate products lock current rates but lose if rates rise. Moving money between accounts to chase the best rate has limited value once you've secured a competitive rate — switching from 4.7% to 5.0% on 20,000 saves 60/year, typically not worth the paperwork and tracking complexity. Switching from 2.5% to 4.7% on the same amount saves 440/year — yields clear net benefit.

The rule of thumb: if your rate is within 0.5% of top market rates, don't bother switching. If it's 1%+ off, switch. Between 0.5-1%, depends on amount and inconvenience.

The bonus-rate trap

Many easy-access accounts offer "bonus rates" that expire after 12 months. A 5.2% rate for 12 months then 0.8% thereafter is common. If you'll remember to switch at month 11, this works. If you won't, the effective 2-year rate might be around 3% — significantly less attractive. Automatic reminders at month 10 to review rates is the simple discipline that makes bonus rates worth using.

Fixed-rate bonds: when to lock in

Fixed-rate bonds trade flexibility for rate certainty. Current 1-year rates around 4.8%, 5-year around 4.5%. The inverted curve (shorter rates higher than longer) reflects market expectations that rates will fall. Locking in a 5-year rate at 4.5% applies if you expect rates to be below 4.5% for most of the next 5 years. If rates stay at 4.5%+ for most of the period, you've given up flexibility for no premium. Most savers benefit from a mix: keep emergency fund easy-access, consider 1-2 year fixed for cash reserves you won't need, leave longer-horizon money for equity-based products.

What this calculator shows

The tool projects savings growth based on rate, compounding frequency, and time horizon. It doesn't automatically model tax implications, PSA usage, or comparison against investment alternatives. Use the figure as the gross projection; subtract expected tax for net outcome; compare against investment alternatives for appropriate holding periods.