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Split the windfall
The amount, what you owe, your emergency-fund gap, and how much retirement room you have left this year.
TOOL · MONEY
Windfall Allocation Calculator
A bonus, an inheritance, a tax refund — sudden money evaporates fast without a plan. This calculator runs your windfall through the priority waterfall: fun money first (so the plan sticks), then your emergency-fund gap, then high-interest debt, then unused retirement room, and the rest into a taxable investment.
How the waterfall works
The allocation follows one fixed priority order — every dollar flows down the waterfall, and a bucket only takes what’s left after the buckets above it. This is the same order financial planners teach, just arithmetic: it guarantees the money hits the highest-return use first instead of the most tempting one.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Fun money | W × fun% | $2,500 of the $25,000 — the deliberate splurge that keeps you from raiding the serious buckets later. |
| Emergency fund | min(gap, remainder) | $6,000 — your full emergency gap, filled before anything optional. |
| High-interest debt | min(debt, remainder) | $8,000 — the whole credit-card balance, wiped at its 20%+ rate. |
| Retirement accounts | min(room, remainder) | $7,000 — the remaining retirement room, filled. |
| Taxable investment | remainder | $1,500 — what’s left after the first four buckets, into a brokerage account. |
Why fun money goes first
Putting the splurge first is not generosity — it’s engineering. Windfalls feel like free money, and a plan that bans all spending is a plan you’ll abandon by Friday. Carving out a fixed slice up front (10% is the usual starting point) buys your compliance with the boring, high-return buckets below it. The bucket is capped at 30% here: if you want to blow more than that, you don’t have a windfall problem, you have a spending problem.
Who uses this
- Bonus season: an annual bonus lands — decide the split before the money feels spendable.
- Inheritance recipients: a life event brings a lump sum — the waterfall keeps grief and impulse apart.
- Tax-refund optimists: that refund is a windfall, not a windfall-shaped excuse — run it through the same waterfall.
- Side-hustle windfalls: a big freelance month or a sold car — split it before lifestyle absorbs it.
Accuracy & limitations
This is an allocation heuristic, not tax advice: inheritance and bonus tax treatment differ (bonuses are ordinary income, inheritances generally aren’t income to the recipient), and the waterfall ignores timing — 401(k) room expires with the calendar year, debt keeps compounding daily. Enter after-tax dollars: if the windfall is a pre-tax bonus, subtract the taxes first or you’ll allocate money the IRS already claimed.
The full reasoning — including the tax primer and the three classic mistakes — is in the guide How to allocate a windfall.
Cite this calculatorBright Side Kit. “Windfall Allocation Calculator.” brightoolbox.com, 2026.
Bright Side Kit. "Windfall Allocation Calculator." https://brightoolbox.com/windfall-allocation-calculator/ Accessed October 22, 2026.Frequently asked questions
Should I pay off debt or invest my windfall first?
Pay high-interest debt first — a 22% credit card is a guaranteed 22% return, which no investment reliably beats. The waterfall handles it automatically: debt sits above retirement and taxable investing precisely because the guaranteed return is higher. Low-rate debt (a 3% mortgage) can stay; the calculator only asks for the high-interest pile.
Is a tax refund really a windfall?
Functionally, yes — it’s a lump of after-tax cash you didn’t budget around. Most people spend refunds by feel and remember none of it a year later. Running it through the waterfall turns it into emergency-fund progress or killed debt instead of evaporated money.
Do I owe tax on an inheritance?
Generally no income tax to you as the recipient — inheritances aren’t income. (Estates above the very large federal exemption can owe estate tax, but that’s paid by the estate, not you.) Bonuses and most other windfalls are ordinary income, so enter those amounts after tax.
What if my windfall doesn’t fill every bucket?
Then the priority order does its job: the top buckets fill completely and the lower ones get what’s left — possibly nothing. A $5,000 windfall with a $6,000 emergency gap fills $4,500 of the gap after fun money; debt and retirement wait for the next windfall. Partial progress at the top of the waterfall beats a thin spread everywhere.
Why only 10% for fun money?
It’s a default, not a rule — adjust it. 10% is the starting point planners suggest because it’s big enough to feel real and small enough not to matter if the windfall was the plan that fixed your finances. The field caps at 30%: above that, you’re not allocating a windfall, you’re spending it.
What counts as high-interest debt?
Roughly 8% and up: credit cards, payday loans, personal loans, most auto loans. The exact cutoff is judgment — if the rate exceeds what you’d confidently earn investing (say 7%), it belongs in the debt bucket.
Can I use this for a married couple’s finances?
Yes — enter combined numbers: the household windfall, household high-interest debt, the shared emergency-fund gap. The one caveat is retirement room: enter your combined unused room, but remember it lives in individual accounts.