Data sources & methodology
Last updated: July 2026
PaydownBase runs entirely in your browser. Payoff dates, interest totals, and loan payments come from documented formulas and Federal Reserve consumer credit benchmarks — not from a black-box API or lender quote engine. This page explains our sources, default assumptions, and known simplifications.
Default assumptions (debt & loan calculators)
- Fixed monthly APR unless you change it — no variable-rate index modeling
- Extra payments apply the same amount every month until the balance reaches zero
- No late fees, penalty APR, or promotional 0% windows unless you model them manually
- Loan calculators use standard fixed-rate PMT amortization (level payment)
- Results are planning estimates — not loan approval, payoff quotes, or legal advice
2026 Fed rate presets (verify at a glance)
| Benchmark | Preset used on site |
|---|---|
| Avg credit card APR (accounts assessed interest) | 21.52% (Fed G.19, Q1 2026) |
| New car loan APR (60-month) | 7.14% (Fed G.19, 2026-05 preliminary) |
| Used car loan APR (typical planning preset) | 9.25% (above new-car average; shop your rate) |
| Subprime auto loan APR (planning range) | 12–18% (varies widely by lender and term) |
| Personal loan APR (24-month, bank) | 11.86% (Fed G.19, 2026-05 preliminary) |
You can override any preset with your own APR. Presets follow the Federal Reserve G.19 consumer credit statistical release; preliminary figures are labeled when noted on the tool page.
Primary sources we reference
- Federal Reserve G.19 — Consumer Credit (APR benchmarks) ↗
- NY Fed — Quarterly Report on Household Debt and Credit ↗
- CFPB — Regulation Z (Truth in Lending), minimum payment examples ↗
Core formulas
| Calculator type | Formula |
|---|---|
| Installment loan payment | Standard PMT: fixed payment from principal, monthly rate, and term |
| Amortization schedule | Interest = balance × monthly rate; principal = payment − interest |
| Credit card payoff | Fixed payment amortization on revolving balance at your APR |
| Snowball / avalanche | Sequential payoff: apply freed minimums + extra to next target debt |
Known simplifications by tool
Debts are modeled as fixed balances with monthly APR converted to a monthly periodic rate. Extra payment is applied after minimums. No late fees, penalty APR resets, or promotional 0% windows unless you enter them manually.
Uses standard amortization on a revolving balance with a fixed monthly payment you specify. Minimum-payment rules from card issuers vary; our minimum-payment helper follows common percentage-plus-floor patterns, not your exact card agreement.
Monthly payment uses the standard PMT formula on a fixed-rate installment loan. Sales tax, dealer fees, gap insurance, and prepayment penalties are not included unless noted in advanced fields.
Front-end and back-end ratios use the debts and income you enter. Lender underwriting may count debts or income differently than this planning estimate.
How we update & verify
- When the Federal Reserve publishes new G.19 consumer credit averages, we update default APR presets and note the release month on affected calculators.
npm run buildruns automated regression tests on loan, debt, and credit-card math engines.- We spot-check amortization and payoff examples against hand-calculated schedules before deploy.
- This page's date is updated when presets or formulas change materially.
Report an error
Wrong Fed preset, payoff order bug, or amortization that does not match the documented formula? Email contact@paydownbase.com. We treat incorrect rate data and math errors as production incidents on YMYL content. Last verified: July 2026.
See also About for what PaydownBase is — and is not.
Rate presets and formulas last updated: July 2026. Sources & methodology
Found a wrong number? Email contact@paydownbase.com — corrections ship fast. See also About and Terms.