Sinking Fund Payment Calculator (Save-to-Target)
Enter the future value you want to reach (e.g. $1,000,000 in 30 years), an expected annual return and a savings term — the calculator back-solves how much you need to deposit each period to hit the target on time. Supports monthly or yearly deposits and ordinary (end-of-period) or annuity-due (start-of-period) timing. It is the inverse of the FV-of-annuity formula, the same back-solve as Excel/Google Sheets PMT(). Common uses: house down payments, college funds, retirement targets, and bond sinking funds reserved by issuers to retire debt at maturity.
Please enter a valid number
Required payment per period
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Contributions (paid in total)
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Interest / return (compounded)
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Back-solves PMT = FV × r / ((1 + r)ⁿ − 1) for the required deposit, assuming a flat pre-tax rate and ignoring fees. Real-world returns fluctuate; trim the rate by 1–2% for a conservative plan.
Formula
PMT = FV × r / ((1 + r)ⁿ − 1) (ordinary, end-of-period) PMT_due = PMT_ordinary / (1 + r) (annuity-due, start-of-period) r = i / k, n = years × k k = 12 (monthly), 1 (yearly); when r = 0 the formula collapses to PMT = FV / n
- · The return rate is assumed to be a constant geometric average — equities ~6–8%, balanced funds ~4–5%, fixed deposits / investment-grade bonds ~2–4% as rough guides. Real-world returns fluctuate year to year, so the result is a planning estimate rather than a guarantee.
- · Annuity-due deposits each earn one extra period of interest, so for the same target you can save roughly r / (1 + r) less per period — about 0.5% lighter for 30-year monthly contributions at 6%.
- · When r = 0 the formula collapses to PMT = FV / n (just split the target evenly). The tool handles this edge case explicitly so the result never goes to NaN.
- · The output is a nominal figure (ignores inflation). To hit "today's purchasing power equivalent of $1,000,000", multiply the target by (1 + inflation)^years first, or enter a real return rate (nominal − inflation) directly.
- · The URL is updated with g (goal), r (rate), y (years), f (frequency), t (timing) so you can bookmark or share a specific scenario.
- · Cross-checked against Excel / Google Sheets PMT(rate, nper, 0, -FV, type) with type = 0 (ordinary) or type = 1 (annuity-due).
Frequently asked
How is this different from the Future Value of Annuity Calculator?
They are inverses of one another. The FV-of-annuity calculator asks "if I save PMT per month for n years, how much will I have?" and outputs the FV. The sinking-fund tool asks "if I want FV after n years, how much must I save per month?" and outputs the PMT. Both use the same formula FV = PMT × ((1 + r)ⁿ − 1) / r — just with the known and unknown swapped. Use the FV one when you start from your savings rate; use this one when you start from a target.
Why is it called a "sinking fund"?
The name comes from 18th-century British Treasury practice: to "sink" a national debt by retirement date, the government set aside a fixed sum each year that compounded into exactly the bond's face value by maturity. Corporate accounting still uses "sinking fund" for any plan that funnels periodic deposits into a target balance via compounding. In personal finance, a house down-payment plan, college fund, retirement nest egg or AVD reserve are all sinking funds in disguise.
What if I can increase my deposits mid-way as my salary grows?
The tool assumes a level (constant) payment. If you expect to ramp deposits up as your salary grows (an escalating sinking fund), you will hit the target faster than this estimate — or you can start with a smaller monthly figure. A simple workaround: rerun the calculator every few years with the remaining target and your new payment level. For complex scenarios (e.g. salary +3% per year linearly), stitch together segments using this tool plus the FV-of-annuity calculator.
What happens if I enter 0% return?
The formula automatically collapses to PMT = FV / n — i.e. it just splits the target evenly across all periods. For example, a $120,000 target over 10 yearly deposits at 0% gives $12,000/year, or $1,000/month for monthly. In practice this is equivalent to stuffing cash into a 0%-interest account, which is rarely realistic but helps you appreciate the power of compounding: hitting a $1,000,000 target over 30 years takes $2,778/month at 0% but only $1,201/month at 5% — about a 2.3× difference.
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