Savings interest calculator

See what a rate of your choosing earns on a savings deposit: the interest, the final balance and how the credits build up. Choose easy-access, where you set how often interest is added, or fixed-term over a set number of months, and add a comparison rate to see the difference side by side. The calculator holds no market rates and compares no providers — the rate is always your own. Everything runs in your browser; nothing is stored or sent.

This calculator needs JavaScript because the calculation runs entirely in your browser – so your inputs never leave your device. Two fully worked examples are shown further down this page.

What your result means

The final balance is your deposit plus all the interest credited over the term; interest earned is the difference. The effective annual rate turns the whole result into a single yearly figure — the rate that, compounded once a year, would give the same balance.

With a comparison rate, the calculator also shows what a second rate would produce and the gap between the two, so you can see what a difference in the rate alone makes.

The schedule below lists each interest credit and the running balance.

How this calculator works

The calculator works in whole months. Interest is credited at the chosen interval and then earns interest itself. The period rate is the annual rate times the interval length in months, divided by twelve.

For easy-access you choose the crediting interval — monthly, quarterly or annually. A part-period left over at the end earns simple, pro-rata interest, so at a term of exactly one month every interval gives the same result.

For fixed-term you choose between annual crediting (compound) and simple interest paid at maturity over the whole term. The effective annual rate shown alongside is worked out purely from the opening and closing balance — it is not a market figure. Internally the calculation is unrounded and only rounded to the nearest penny for display.

Formula and variables

Final balance = D · (1 + i·L/12)^g · (1 + i·rest/12)Easy-access: L = 1 (monthly), 3 (quarterly) or 12 (annually)Fixed-term compound: L = 12 · Fixed-term simple: Final = D · (1 + i·months/12)Interest earned = Final balance − D

D: Deposit amount
i: Annual interest rate as a decimal (3% is 0.03)
L: Length of the crediting interval in months
g: Number of full crediting intervals
rest: Part-period months at the end (simple, pro-rata interest)
months: Total term in months

Worked examples

Example 1: a fixed-term deposit with annual compounding

Example inputs
Account type	Fixed-term
Deposit	€8,000.00
Interest rate (example assumption)	4% p.a.
Duration	36 months
Interest crediting	Annually (compound)

Example results
Final balance	€8,998.91
Interest earned	€998.91
Effective annual rate	4.00%

With annual crediting the €8,000.00 grows over three years: €8,000.00 × 1.04^3 ≈ €8,998.91, so €998.91 is interest. At simple interest paid at maturity it would be €8,000.00 × 0.04 × 3 = €960.00 instead. Because the rate compounds once a year, the effective annual rate here equals the 4% nominal rate. The 4% is an example assumption, not a current market rate.

Example 2: easy-access with a comparison rate

Example inputs
Account type	Easy-access
Deposit	€15,000.00
Interest rate (example assumption)	3% p.a.
Duration	18 months
Interest crediting	Monthly
Comparison rate	4% p.a.

Example results
Final balance at 3%	€15,689.54
Final balance at 4%	€15,925.96
Difference	€236.42

With monthly crediting over 18 months, 3% turns €15,000.00 into €15,689.54, while 4% gives €15,925.96 — a gap of €236.42 from the higher rate alone. Because interest is credited monthly, the effective annual rate at 3% is about 3.04%, a little above the nominal figure. Both rates are example assumptions; real easy-access rates can change at any time.

Assumptions

The interest rate stays constant in the scenario — for easy-access this is deliberately unrealistic (rates vary).
The deposit stays the same over the term (no top-ups or withdrawals).
Interest is credited at the chosen interval and then earns interest; a part-period at the end earns simple, pro-rata interest.
Tax and inflation are not included.

Limitations of this calculator

No market rates, no provider data and no product comparison — the rate is your own input.
Easy-access rates are variable in reality; the constant-rate assumption is a simplification.
Deposit protection and account terms are mentioned only in words, not calculated.
Tax on interest is not applied (version 1 calculates without tax).

Common misconceptions

Treating the rate as a market figure: The rate is your assumption, not a live or guaranteed savings rate. Real offers change and vary by provider.
Assuming easy-access rates hold: Easy-access rates are variable and can change at any time; a constant rate is only a scenario.
Confusing effective and nominal rate: When interest compounds during the year, the effective annual rate sits above the nominal rate you entered.
Reading protection into the result: Deposit protection limits and account terms are not part of the maths — check them separately.

Frequently asked questions

Does it show current savings rates?

No. The calculator holds no market rates and compares no providers. You enter the rate yourself — from a specific offer, or as your own assumption — so the figures stay neutral and independent of the day's deals.

What is the difference between easy-access and fixed-term here?

For easy-access you pick how often interest is credited (monthly, quarterly or annually); the rate is held constant in the scenario but is variable in reality. For fixed-term you set a term and choose between annual compounding and simple interest paid at maturity.

Why is the effective annual rate higher than the rate I entered?

When interest is credited during the year and then earns interest itself, the effective annual rate — the AER-style figure — sits above the nominal rate. The value shown is worked out from the opening and closing balance; it is a calculation, not a quoted product rate.

Do easy-access rates really stay the same?

Usually not. Easy-access rates are variable and can change at any time. The calculator holds the rate steady so you can model one scenario; reality will differ, and over longer periods the gap can be large.

Is deposit protection or tax included?

No. Protection schemes and their limits vary by country and are not part of the calculation, and tax on interest is not applied — check the terms of any specific account, and your own tax position, separately.

Sources and further reading

Official and independent sources on this topic. The links open each website in a new tab; no content is loaded from them into this page.

Equivalent and Effective Interest RatesMathematics LibreTexts (Business Mathematics, J. Olivier)Reference for the effective annual rate — the true annually-compounded rate equivalent to interest compounded more often.
Compound Interest CalculatorU.S. Securities and Exchange Commission (Investor.gov)Official tool showing how a savings balance grows as interest is added and then earns interest itself.

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Last reviewed: 26/07/2026 · All calculations run in your browser – inputs are not stored. ·How we check our calculators