INPUT AND EVIDENCE LEDGER
Put the two cases on the same footing.
| Field | Value | Origin |
|---|---|---|
| Principal | ₩300,000,000 | Controlled comparison input |
| 10-year endpoint | 4.90% fixed / 120 payments | HF September 2026 published rate |
| 50-year endpoint | 5.20% fixed / 600 payments | HF September 2026 published rate |
| Repayment | Equal monthly principal and interest | APT calculation rule |
DECISION READING
Read the gap, not just the winner.
The 50-year endpoint cuts the scheduled payment by about 56%, but the modeled lifetime interest is about ₩462.9M higher. The lower monthly figure cannot be presented without the term and total-payment layer.
REPRODUCIBLE WORK
The comparison ledger.
| Check | Formula or rule | Result |
|---|---|---|
| 10-year payment | P × r(1+r)^n ÷ ((1+r)^n−1) | ₩3,167,322 per month |
| 50-year payment | Same formula; 600 periods at 5.20% | ₩1,404,938 per month |
| Monthly relief | ₩3,167,322 − ₩1,404,938 | ₩1,762,384 |
| Scheduled interest | Total scheduled payments − ₩300M | ₩80.1M over 10 years versus ₩543.0M over 50 years |
SOURCE SNAPSHOT
The official values behind the comparison.
SENSITIVITY
Conditions that can reverse the gap.
- Eligibility, age, property value, and product rules can make one term unavailable.
- Early repayment would change the lifetime-interest comparison.
- The two rates are official endpoint rates, not a quote for this borrower.
OWNER AUTHORIZATION + VERIFICATION RECORD
One accountable operator and a reproducible check record.
The TOOOLBOX site owner authorized this publication scope and remains the correction contact. The checks below were completed during preparation with AI-assisted implementation; they are an audit record, not a claim of licensed professional review.
- Review ID
- TB-APT-10-20260902
- Owner role
- TOOOLBOX site owner and developer
- Release scope
- Owner-authorized · 2026-09-02
- Correction channel
- Public contact page
- Opened the HF release and matched both endpoint rates and terms.
- Recomputed all 120- and 600-period payment totals independently.
- Added eligibility and early-repayment boundaries before publication.
BOUNDARIES
Claims this comparison cannot support.
- This calculation excludes fees, insurance, prepayment charges, and underwriting.
- It does not recommend a term or establish eligibility.
- Rates can change after the cited September 2026 publication.
MORE APT DECISION NOTES
Compare another evidence pattern.
The related notes deliberately use different questions, data states, and editorial forms.