Calculator
Large screens: 3 columns. Smaller: 2 columns. Mobile: 1 column.
Example Data Table
Use this dataset to verify the calculator quickly.
| Scenario | Loan | Rate | Term | Extra | Lump Sum | Method | Expected outcome |
|---|---|---|---|---|---|---|---|
| Sample A | $250,000 | 6.50% | 30 years | $0 | $0 | Half of monthly | Earlier payoff, lower total interest |
| Sample B | $120,000 | 5.25% | 15 years | $75 | $2,500 at month 6 | Half of monthly | More months saved, bigger interest reduction |
| Sample C | $30,000 | 0.00% | 5 years | $0 | $0 | Equivalent biweekly | Payoff time similar to monthly |
Tip: set “Show schedule preview tables” to see the first rows.
Formula Used
Daily interest makes biweekly timing more realistic.
- Daily rate: r_d = (APR / 100) / 365
- Interest for a period: Interest = Balance × r_d × Days
- Principal paid: Principal = Payment − Interest (extra principal is added directly to principal)
- New balance: NewBalance = Balance − Principal
- Computed monthly payment (when using term): P = L × (r_m / (1 − (1 + r_m)^−n)), where r_m = APR/12 and n = years×12
- Biweekly options: P_bi = P/2 (accelerated) or P_bi = P×12/26 (equivalent yearly total)
How to Use This Calculator
A quick workflow for accurate what‑if planning.
- Enter your loan amount, APR, and loan start date.
- Pick Input mode: loan term to compute payment, or your current monthly payment.
- Choose a Biweekly method: accelerated half-payment or equivalent biweekly.
- Add optional extra principal and a one-time lump sum with date.
- Click Calculate to compare payoff dates and interest.
- Use CSV/PDF downloads to save the full schedules.