Discount Points Buydown Breakeven Months Calculator

Route actual caller matched baseline/buydown payment ledgers against exact points+incremental closing cost, reversals/horizon retained; no constant savings, financing/holding-period or tax assumptions. Caller independently verifies edition, jurisdiction, applicability and one currency; screening does not establish legal compliance, coverage or bank approval.

Description

Discount points exchange additional closing cost for a different payment schedule.

Discount points exchange additional closing cost for a different payment schedule.^[1]

Observed break-even depends on the cumulative matched payments and the comparison horizon. Use Discount Points Buydown Breakeven Months Calculator to evaluate the supplied inputs under the model explained below.

When to use Discount Points Buydown Breakeven Months Calculator

Use Discount Points Buydown Breakeven Months Calculator to evaluate the supplied inputs under the model explained below. Establish the currency and minor-unit convention, measurement period and applicable transaction or institution context.

How to use Discount Points Buydown Breakeven Months Calculator and understand its results

Establish the currency and minor-unit convention, measurement period and applicable transaction or institution context.
Enter Caller loan principal minor, Caller discount points bps, Caller other incremental closing minor, Caller monthly baseline payments minor, Caller monthly bought down payments minor using the field table and validation rules below, then run the tool.
Read Caller incremental closing cost minor, Cumulative signed buydown savings minor, First observed buydown break even month; interpret the units, signs, ordering and unknown-value placeholders described below.
Correct reported input errors and rerun. Apply successful results according to their specific meanings and check the assumptions before using them in a decision.

Input field	Meaning	Value type	Requirement
callerLoanPrincipalMinor	Caller loan principal minor	number	Required; constraints below
callerDiscountPointsBps	Caller discount points bps	number	Required; constraints below
callerOtherIncrementalClosingMinor	Caller other incremental closing minor	number	Required; constraints below
callerMonthlyBaselinePaymentsMinor	Caller monthly baseline payments minor	array of number	Required; constraints below
callerMonthlyBoughtDownPaymentsMinor	Caller monthly bought down payments minor	array of number	Required; constraints below

Enter principal and incremental closing cost as nonnegative integer minor units up to 1000000000000, points as integer 0–10000 basis points and nonempty aligned monthly payment arrays of at most 600 entries in the monetary range. Round principal×points/10000 to nearest minor unit, halves away from zero, and add incremental cost. Start cumulative savings at negative closing cost and add baseline−boughtDown each month. Return the first supplied month with savings≥0, one based, or −1 if none. No interest schedule, discount rate or benefit after the supplied horizon is inferred.

closing=round(principal×pointsBps/10000)+otherClosing; savings[m]=−closing+Σ(baseline−boughtDown)

Use the field order, units and branch conditions described above.

Output field	Meaning	Value type
callerIncrementalClosingCostMinor	Caller incremental closing cost minor	number
cumulativeSignedBuydownSavingsMinor	Cumulative signed buydown savings minor	array of number
firstObservedBuydownBreakEvenMonth	First observed buydown break even month	number

json

{
  "input": {
    "callerLoanPrincipalMinor": 10000,
    "callerDiscountPointsBps": 100,
    "callerOtherIncrementalClosingMinor": 50,
    "callerMonthlyBaselinePaymentsMinor": [
      100,
      100,
      100
    ],
    "callerMonthlyBoughtDownPaymentsMinor": [
      50,
      50,
      50
    ]
  },
  "output": {
    "callerIncrementalClosingCostMinor": 150,
    "cumulativeSignedBuydownSavingsMinor": [
      -100,
      -50,
      0
    ],
    "firstObservedBuydownBreakEvenMonth": 3
  }
}

Limitations and assumptions

Observed break-even depends on the cumulative matched payments and the comparison horizon. Apply the exact scope and assumptions explained above.

All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse arrays fail validation. Domain-specific bounds, alignments and supported tokens are explained above; extremely large inputs or outputs can also be rejected. Input errors differ from successful false results, empty match lists and unknown-evidence placeholders.

Alternative or Complementary methods

Use Balance Transfer Break Even Months Calculator for a related task: A balance transfer changes interest charges while introducing an upfront cost.

Use Card Minimum Payment Months Payoff Calculator for a related task: A card minimum-payment schedule combines interest, a balance-based minimum and a floor.

References

Discount Points Buydown Breakeven Months Calculator — tool.io

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