Personal Finance · Evidence and source dates listed below
What changes mathematically between avalanche and snowball?
Compare modeled interest and completion dates under identical assumptions.
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Full briefing transcript
Two repayment orders can finish in the same month and still cost different amounts. Our fictional debts total five thousand dollars, and both plans use three hundred dollars a month. Under the exact fixed-rate model we will show, avalanche adds eight hundred two dollars twenty-nine in interest. Snowball adds eight hundred sixty-two dollars forty-eight. Both finish in month twenty. The answer is a cost comparison, not a universal winner or payoff promise.
Make the comparison fair before trusting a calculator result. A opens at five hundred dollars and ten percent; B at fifteen hundred and twenty-five percent; C at three thousand and eighteen percent. Required teaching payments are twenty-five, forty-five, and seventy. Both plans charge monthly interest before payment, round each debt charge to cents, make no new purchases, and retain the same total budget. Only the extra-payment priority changes between the plans.
In month one, interest charges are identical: four dollars seventeen, thirty-one dollars twenty-five, and forty-five. Avalanche pays A twenty-five, B two hundred five, and C seventy. Snowball pays A one hundred eighty-five, B forty-five, and C seventy. The extra one hundred sixty is moved, not invented. Month-one interest is the same because the opening balances are the same; later interest differs because the ending balances take different paths.
We then repeat the same calculation for every modeled month. Avalanche finishes B in month nine, redirects the unused money that month, and finishes all debt in month twenty. Snowball finishes A in month three, B in month ten, and all debt in month twenty. The complete original schedules accompany this briefing. On screen, selected checkpoints show those closures; they are not a substitute for the recurrence or a claim about actual bank posting dates.
Add the charges rather than multiplying the monthly budget by twenty. Avalanche pays five thousand eight hundred two dollars twenty-nine in total; its final month needs only one hundred two dollars twenty-nine. Snowball pays five thousand eight hundred sixty-two dollars forty-eight; its final month needs one hundred sixty-two dollars forty-eight. The difference is sixty dollars nineteen. An unused final-month budget is not an additional payment, interest charge, or fee.
Use identical assumptions when comparing modeled interest and completion dates. If rates, fees, payment amounts, timing, or new borrowing differ, you are comparing more than order. Real agreements and a sustainable due-date plan still matter, and this simplified monthly model is not an issuer payoff quote. This is general education, not individualized financial advice. The next briefing shows what changes when a finished payment is kept in the repayment budget rather than removed.
Practical takeaway
Compare modeled interest and completion dates under identical assumptions.
Exact approved fictional calculation record
This source-pinned teaching model is reproduced without changing its values.
{
"label": "FICTIONAL FIXED-RATE AMORTIZATION — NOT ISSUER QUOTES",
"columns": [
"Debt",
"Opening balance",
"Fixed annual rate",
"Required monthly amount"
],
"rows": [
[
"A",
"$500",
"10%",
"$25"
],
[
"B",
"$1,500",
"25%",
"$45"
],
[
"C",
"$3,000",
"18%",
"$70"
]
],
"models": {
"avalanche": {
"months": 20,
"interestCents": 80229,
"feesCents": 0,
"totalPaidCents": 580229,
"rows": [
{
"month": 1,
"interestCents": [
417,
3125,
4500
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
47917,
132625,
297500
]
},
{
"month": 2,
"interestCents": [
399,
2763,
4463
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
45816,
114888,
294963
]
},
{
"month": 3,
"interestCents": [
382,
2394,
4424
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
43698,
96782,
292387
]
},
{
"month": 4,
"interestCents": [
364,
2016,
4386
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
41562,
78298,
289773
]
},
{
"month": 5,
"interestCents": [
346,
1631,
4347
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
39408,
59429,
287120
]
},
{
"month": 6,
"interestCents": [
328,
1238,
4307
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
37236,
40167,
284427
]
},
{
"month": 7,
"interestCents": [
310,
837,
4266
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
35046,
20504,
281693
]
},
{
"month": 8,
"interestCents": [
292,
427,
4225
],
"paymentCents": [
2500,
20500,
7000
],
"endingBalanceCents": [
32838,
431,
278918
]
},
{
"month": 9,
"interestCents": [
274,
9,
4184
],
"paymentCents": [
2500,
440,
27060
],
"endingBalanceCents": [
30612,
0,
256042
]
},
{
"month": 10,
"interestCents": [
255,
0,
3841
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
28367,
0,
232383
]
},
{
"month": 11,
"interestCents": [
236,
0,
3486
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
26103,
0,
208369
]
},
{
"month": 12,
"interestCents": [
218,
0,
3126
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
23821,
0,
183995
]
},
{
"month": 13,
"interestCents": [
199,
0,
2760
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
21520,
0,
159255
]
},
{
"month": 14,
"interestCents": [
179,
0,
2389
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
19199,
0,
134144
]
},
{
"month": 15,
"interestCents": [
160,
0,
2012
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
16859,
0,
108656
]
},
{
"month": 16,
"interestCents": [
140,
0,
1630
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
14499,
0,
82786
]
},
{
"month": 17,
"interestCents": [
121,
0,
1242
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
12120,
0,
56528
]
},
{
"month": 18,
"interestCents": [
101,
0,
848
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
9721,
0,
29876
]
},
{
"month": 19,
"interestCents": [
81,
0,
448
],
"paymentCents": [
2500,
0,
27500
],
"endingBalanceCents": [
7302,
0,
2824
]
},
{
"month": 20,
"interestCents": [
61,
0,
42
],
"paymentCents": [
7363,
0,
2866
],
"endingBalanceCents": [
0,
0,
0
]
}
]
},
"snowball": {
"months": 20,
"interestCents": 86248,
"feesCents": 0,
"totalPaidCents": 586248,
"rows": [
{
"month": 1,
"interestCents": [
417,
3125,
4500
],
"paymentCents": [
18500,
4500,
7000
],
"endingBalanceCents": [
31917,
148625,
297500
]
},
{
"month": 2,
"interestCents": [
266,
3096,
4463
],
"paymentCents": [
18500,
4500,
7000
],
"endingBalanceCents": [
13683,
147221,
294963
]
},
{
"month": 3,
"interestCents": [
114,
3067,
4424
],
"paymentCents": [
13797,
9203,
7000
],
"endingBalanceCents": [
0,
141085,
292387
]
},
{
"month": 4,
"interestCents": [
0,
2939,
4386
],
"paymentCents": [
0,
23000,
7000
],
"endingBalanceCents": [
0,
121024,
289773
]
},
{
"month": 5,
"interestCents": [
0,
2521,
4347
],
"paymentCents": [
0,
23000,
7000
],
"endingBalanceCents": [
0,
100545,
287120
]
},
{
"month": 6,
"interestCents": [
0,
2095,
4307
],
"paymentCents": [
0,
23000,
7000
],
"endingBalanceCents": [
0,
79640,
284427
]
},
{
"month": 7,
"interestCents": [
0,
1659,
4266
],
"paymentCents": [
0,
23000,
7000
],
"endingBalanceCents": [
0,
58299,
281693
]
},
{
"month": 8,
"interestCents": [
0,
1215,
4225
],
"paymentCents": [
0,
23000,
7000
],
"endingBalanceCents": [
0,
36514,
278918
]
},
{
"month": 9,
"interestCents": [
0,
761,
4184
],
"paymentCents": [
0,
23000,
7000
],
"endingBalanceCents": [
0,
14275,
276102
]
},
{
"month": 10,
"interestCents": [
0,
297,
4142
],
"paymentCents": [
0,
14572,
15428
],
"endingBalanceCents": [
0,
0,
264816
]
},
{
"month": 11,
"interestCents": [
0,
0,
3972
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
238788
]
},
{
"month": 12,
"interestCents": [
0,
0,
3582
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
212370
]
},
{
"month": 13,
"interestCents": [
0,
0,
3186
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
185556
]
},
{
"month": 14,
"interestCents": [
0,
0,
2783
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
158339
]
},
{
"month": 15,
"interestCents": [
0,
0,
2375
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
130714
]
},
{
"month": 16,
"interestCents": [
0,
0,
1961
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
102675
]
},
{
"month": 17,
"interestCents": [
0,
0,
1540
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
74215
]
},
{
"month": 18,
"interestCents": [
0,
0,
1113
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
45328
]
},
{
"month": 19,
"interestCents": [
0,
0,
680
],
"paymentCents": [
0,
0,
30000
],
"endingBalanceCents": [
0,
0,
16008
]
},
{
"month": 20,
"interestCents": [
0,
0,
240
],
"paymentCents": [
0,
0,
16248
],
"endingBalanceCents": [
0,
0,
0
]
}
]
}
},
"comparison": [
[
"Avalanche",
"$802.29",
"$5,802.29",
"End month 20"
],
[
"Snowball",
"$862.48",
"$5,862.48",
"End month 20"
]
],
"difference": "$862.48 - $802.29 = $60.19"
}Approved assumptions
[ "All debts, households and inputs are fictional US educational examples; no private finances, real offer or individualized recommendation.", "A $500 at 10%, B $1,500 at 25%, C $3,000 at 18%; fixed nominal annual rates. Monthly model uses APR/12, charges interest before end-month payment and rounds each debt charge half-up to cents. It is not an issuer daily-balance calculation.", "Required amounts A $25, B $45, C $70 are invented fixed teaching inputs, not actual minimum formulas; cap each at the amount owed. No new purchases, fees, rate changes, grace periods or prepayment penalties unless an episode expressly introduces one.", "Extra funds go in stated priority after required payments. Unused payoff-month funds move immediately to the next active target in that same modeled month; total monthly budget is held constant until final payment, which is capped at amount owed.", "Completion means end of the counted modeled month, not a lender payoff quote or calendar-date guarantee. Real allocation rules, posting dates and contractual terms must be verified separately." ]
Educational disclaimer
Short Briefing provides general educational information, not individualized financial, investment, tax, legal, or accounting advice. It does not recommend any particular product, account, security, transaction, or strategy. Circumstances and product terms differ; verify current information and consult an appropriately qualified professional before making consequential financial decisions.
Disclosures
AI-assisted production and synthetic narration. Original teaching examples and diagrams; linked third-party sources retain their respective rights.
Original sources and limits
- https://files.consumerfinance.gov/f/documents/cfpb_your-money-your-goals_debt-action-plan_tool_2018-11.pdf 2026-09-18
Method definitions, extra after minimums, payment rollover and qualitative motivation/cost tradeoff. Does not validate invented model totals or recommend one universal method.
- https://www.consumerfinance.gov/consumer-tools/educator-tools/your-money-your-goals/toolkit/ 2026-09-18
Educational framework for income, bills, debt decisions. No official affordability threshold or product recommendation inferred.
- https://www.consumerfinance.gov/ask-cfpb/how-does-my-credit-card-company-calculate-the-amount-of-interest-i-owe-en-51/ 2026-09-18
Daily-balance mechanics may differ from our explicitly fictional APR/12 monthly model.
- https://www.consumerfinance.gov/ask-cfpb/what-should-i-do-if-i-cant-pay-my-credit-card-bills-en-1697/ 2026-09-18
Contact card company promptly about inability to pay; no guaranteed arrangement or fee waiver.