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
Annual funding shortfall
$22,286
Required annual reserve contribution
$64,286
Approximate percent funded
49%
Needed monthly reserve dues per unit
$89.29
Current monthly reserve dues per unit
$58.33
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter number of units in association.
- 2Enter total future replacement costs (all components) ($).
- 3Enter weighted average remaining life (years).
- 4Enter current reserve fund balance ($).
- 5Enter current annual reserve contribution ($).
- 6Read your annual funding shortfall on the right — it updates as you type.
- 7Hit Share to keep the scenario or send it to someone.
About this calculator
A reserve study estimates the future cost of replacing shared components — roofs, paving, siding, pools, elevators — and how much the association needs to save each year to be ready when those bills come due. This calculator applies the straight-line 'component method' at a portfolio level: total future replacement costs across all components, spread over their remaining lives, compared against current reserve contributions and existing reserve fund balance. Associations that are 'underfunded' (commonly below 70% funded per common reserve study benchmarks) usually face large special assessments right when a big-ticket item fails, which is exactly the outcome adequate reserves are meant to prevent.
Worked example
Using the values the calculator loads with:
Inputs
- Number of units in association: 60
- Total future replacement costs (all components): 900000 $
- Weighted average remaining life: 14 years
- Current reserve fund balance: 220000 $
- Current annual reserve contribution: 42000 $
Results
- Annual funding shortfall: $22,286
- Required annual reserve contribution: $64,286
- Approximate percent funded: 49%
- Needed monthly reserve dues per unit: $89.29
- Current monthly reserve dues per unit: $58.33
What each field means
Inputs
- Number of units in association
- The number of units in association used in the calculation. Starts at 60 so you have a working example on load.
- Total future replacement costs (all components) ($)
- The total future replacement costs (all components) used in the calculation, measured in $. Starts at 900000 $ so you have a working example on load.
- Weighted average remaining life (years)
- The weighted average remaining life used in the calculation, measured in years. Starts at 14 years so you have a working example on load. Accepted range: 1–40 years.
- Current reserve fund balance ($)
- The current reserve fund balance used in the calculation, measured in $. Starts at 220000 $ so you have a working example on load.
- Current annual reserve contribution ($)
- The current annual reserve contribution used in the calculation, measured in $. Starts at 42000 $ so you have a working example on load.
Results
- Annual funding shortfall
- 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.
- Required annual reserve contribution
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Approximate percent funded
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Needed monthly reserve dues per unit
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Current monthly reserve dues per unit
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What does 'percent funded' actually mean?
It compares your current reserve balance against where a fully-funded association should be given component ages, on a 0-100% scale. Above 70% is generally considered healthy, 30-70% is borderline, and below 30% is considered high-risk for a special assessment when a major component fails.
How often should a reserve study be updated?
Most state laws and best practice call for a full reserve study every 3-5 years with an annual update in between to reflect actual spending, inflation, and any component replacements already completed. Costs and remaining lives drift enough over a few years that a stale study understates the true need.
What happens if an HOA is underfunded?
The board typically either raises regular dues, levies a special assessment when a component fails, or borrows against future dues — special assessments are the most disruptive because they arrive as a surprise lump-sum bill exactly when owners are least prepared for it, often $2,000-$10,000+ per unit for a major project.
Do reserve fund investment returns matter?
Yes, especially for larger associations — investing reserve funds in FDIC-insured CDs or a conservative money market rather than a zero-interest checking account can meaningfully reduce the required annual contribution over a decade-plus horizon, though most reserve studies conservatively assume low returns to avoid overstating the fund's growth.
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). HOA Reserve Study Funding Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/hoa-reserve-study-funding
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/hoa-reserve-study-funding" target="_blank" rel="noopener">HOA Reserve Study Funding Calculator — RevenueLab</a> (2026).</p>
Source: [HOA Reserve Study Funding Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/hoa-reserve-study-funding) (2026).