Annuity Future Value Calculator
Work out the future value of a regular fixed contribution under compounding, with total contributed and interest earned.
Input Data
Results
At a glance:Annuity Future Value estimates how much a series of equal periodic contributions grows to at the end under compounding. Unlike a lump-sum investment, an annuity emphasises repeated contributions at fixed intervals. This tool uses the ordinary-annuity (end-of-period) model and computes only the future value of the periodic contributions, excluding any initial principal. It is the core tool for monthly savings, regular fund savings plans and retirement contributions: the longer the term and the higher the return, the more pronounced the compounding and the larger the share of interest — the mathematics behind 'start early, stay consistent'. If you also have an initial principal, use the comprehensive Annuity Calculator which includes the starting deposit.
Formula
Periodic rate i = annual rate ÷ contributions per year; total periods n = years × contributions per year.
Future value FV = periodic contribution × [((1 + i)^n − 1) ÷ i].
Total contributions = periodic contribution × n; interest earned = FV − total contributions.
$$FV = PMT \times \dfrac{(1 + i)^n - 1}{i}$$How to Use
- Enter the planned monthly fixed contribution.
- Enter the expected annual rate and contribution term.
- View the end-of-term future value, total contributions and interest earned.
With a monthly contribution of HK$1,000 at 6% annual rate, the future value, total contributions and interest earned at different terms.
| Term | Future value (final) | Total contributions | Interest earned |
|---|---|---|---|
| 6 years | HK$86,409 | HK$72,000 | HK$14,409 |
| 10 years | HK$163,879 | HK$120,000 | HK$43,879 |
| 20 years | HK$462,041 | HK$240,000 | HK$222,041 |
| 30 years | HK$1,004,515 | HK$360,000 | HK$644,515 |
Case Studies
Case 1: 25-year monthly retirement savings
Ms Wong plans to contribute HK$3,000/month to a retirement portfolio at an expected long-term 5% return, for 25 years.
The end future value is about HK$1,786,529, of which total contributions are HK$900,000 and interest about HK$886,529 — interest nearly equals principal. This shows that with a steady return and consistent contributions, over 25 years compounding contributes interest comparable to the capital put in. Of course 5% is an expected return and markets fluctuate; try different rates for optimistic and conservative scenarios.
Case 2: The huge gap of starting 10 years earlier
Same HK$2,000/month at 6% return, compare 'contribute 30 years' vs 'delay and contribute only 20 years'.
30 years gives about HK$2,009,030 (interest ≈ HK$1.289M); 20 years only about HK$924,082 (interest ≈ HK$444k). Starting 10 years late, the final balance is over HK$1.08M less, yet the principal you skipped is only HK$240k — almost all the gap is 'missed compounding growth'. This is the strongest proof that 'time beats amount': rather than wait for a higher income to contribute big, start early with a smaller amount.
FAQ
How does this differ from the Annuity Calculator?
Annuity Future Value computes only the future value of the periodic contributions themselves; the Annuity Calculator additionally lets you enter an initial deposit and includes its compounding too. If you start with no principal and only contribute monthly, the two give the same result.
What rate should I enter?
Enter a reasonable expected long-term annual return. Conservative time deposits about 1%–3%, a balanced portfolio historically about 4%–7%, but past performance is not future. Try several rates to see the gap between optimistic and conservative scenarios.
What is the difference between end-of-period and beginning-of-period contributions?
This tool uses end-of-period (ordinary annuity) — you deposit at the end of each period. With beginning-of-period (annuity due), each contribution earns one period earlier, so the final value is slightly higher. Most monthly savings plans are treated as end-of-period.
Why does a longer term make interest dominate so much?
Compounding lets each early contribution grow longer and earn more. At HK$1,000/month and 6%: 6 years ≈ HK$86,409 (interest ≈ 14k), 10 years ≈ HK$163,879 (≈44k), 20 years ≈ HK$462,041 (≈222k), 30 years ≈ HK$1,004,515 (≈645k). Going from 20 to 30 years adds only 120k of contributions but over 540k more future value — the snowball power of 'time × compounding'.
Why start monthly saving early?
What you lose by starting late is not just principal but the time for compounding to grow. At HK$2,000/month and 6%: 30 years ≈ HK$2,009,030 (interest ≈ 1.289M); if delayed to only 20 years, ≈ HK$924,082 (≈444k). Ten years late costs over 1.08M, while the skipped principal is only 240k — almost all the difference is 'missed compounding'. This shows monthly saving 'early and consistent' beats 'large but late'.
Related Tools
References
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.