Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Save this much per month
$313.90
Weekly equivalent
$72.44
Per biweekly paycheck
$156.95
Amount still needed
$3,200
Total you will contribute
$3,138.96
Interest earned along the way
$61.04
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter total needed ($).
- 2Enter already saved ($).
- 3Enter months until you need it.
- 4Enter savings apy (%).
- 5Read your save this much per month on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Sinking funds turn irregular expenses — insurance premiums, holidays, new tires — into a predictable monthly line item so they never become credit card debt.
Worked example
Using the values the calculator loads with:
Inputs
- Total needed: 3600 $
- Already saved: 400 $
- Months until you need it: 10
- Savings APY: 4 %
Results
- Save this much per month: $313.90
- Weekly equivalent: $72.44
- Per biweekly paycheck: $156.95
- Amount still needed: $3,200.00
- Total you will contribute: $3,138.96
- Interest earned along the way: $61.04
What each field means
Inputs
- Total needed ($)
- The total needed used in the calculation, measured in $. Starts at 3600 $ so you have a working example on load.
- Already saved ($)
- The already saved used in the calculation, measured in $. Starts at 400 $ so you have a working example on load.
- Months until you need it
- The months until you need it used in the calculation. Starts at 10 so you have a working example on load. Accepted range: 1–120.
- Savings APY (%)
- The savings apy used in the calculation, measured in %. Starts at 4 % so you have a working example on load. Accepted range: 0–10 %.
Results
- Save this much per month
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Weekly equivalent
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Per biweekly paycheck
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Amount still needed
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total you will contribute
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Interest earned along the way
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the sinking fund calculator work?
Sinking funds turn irregular expenses — insurance premiums, holidays, new tires — into a predictable monthly line item so they never become credit card debt. The underlying maths is: Monthly = (Goal − saved) ÷ months remaining.
What do I need to enter?
4 values: total needed, already saved, months until you need it, and savings apy. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the save this much per month result mean?
It is returned as a money amount in US dollars and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
Who is this tool for?
It's built for anyone comparing money scenarios before committing — budgeting a payment, sanity-checking a quote, or seeing what a change in rate or term actually costs.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Sinking Fund Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/sinking-fund
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/sinking-fund" target="_blank" rel="noopener">Sinking Fund Calculator — RevenueLab</a> (2026).</p>
Source: [Sinking Fund Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/sinking-fund) (2026).