Debt Payoff Calculator
Compare two monthly payment plans side by side — see the months, total paid and total interest saved by paying more.
輸入資料
計算結果
重點速覽：Compares two fixed monthly payments on the same balance/rate. Monthly interest = balance x annual/12; subtract payment until cleared; outputs months, total paid, total interest per plan, and the 'saved' gap (Plan1 - Plan2). Example: 10,000 at 12%, 400/mo → ~28.0mo, interest ~1,197; 600/mo → ~18.3mo, interest ~972; switching saves ~9.7mo and ~225. Higher payment cuts principal faster, so later interest falls and payoff accelerates — extra payment saves disproportionately. WARNING: Fixed rate, no new spending; payment must exceed monthly interest. Education, not advice.
計算公式
月利率 = 年利率 ÷ 12。
逐月:每月利息 = 剩餘結欠 × 月利率;每月沖減本金 = 每月還款 − 利息。
重複至結欠為零;總利息為各期利息之和,總還款額 = 結欠 + 總利息。
$$r = \dfrac{\text{年利率}\%}{12}\quad(\text{月利率})$$$$\text{每月}:\; \text{利息} = \text{剩餘結欠} \times r,\; \text{沖本金} = \text{還款} - \text{利息}$$$$\text{可還清條件}:\; \text{每月還款} > r \times \text{結欠}$$使用說明
- Enter the debt balance and annual rate.
- Enter two monthly payments (Plan 1 lower, Plan 2 higher).
- View months, total paid, total interest for each, and the saved gap.
以債務結欠 100,000、年利率 18% (信用卡常見水平) 為例，不同每月還款額下的還清月數與總利息 (HK$)。
| 每月還款 | 還清月數 | 總利息 | 總還款額 |
|---|---|---|---|
| 2,000 | 94 個月 | 86,224 | 186,224 |
| 3,000 | 47 個月 | 39,672 | 139,672 |
| 5,000 | 24 個月 | 19,783 | 119,783 |
| 8,000 | 14 個月 | 11,573 | 111,573 |
理財情境案例
案例一：只還接近利息的金額 —— 永遠還不清
陳女士信用卡結欠 50,000、年利率 30%，首月利息 = 50,000 × 30% ÷ 12 = 1,250。若她每月只還 1,200 (低於利息)，結果如何？
由於還款 1,200 < 每月利息 1,250，扣息後本金不減反增，計算器提示「無法還清」—— 這就是最低還款陷阱。
若她改為每月定額還 3,000，則約 22 個月清還，總利息約 15,490、總還款約 65,490。同一筆卡數，「只還接近利息」永遠脫不了身，「定額多還」不足兩年清袋。
案例二：每月多還 2,000，慳息近萬、提早近一年
王先生結欠 80,000、年利率 24%。他比較每月還 4,000 與 6,000 兩種計畫。
還 4,000：約 26 個月清還、總利息約 23,190；還 6,000：約 16 個月清還、總利息約 13,987。
每月多還 2,000，還款期由 26 個月縮短至 16 個月 (提早近一年)，總利息由約 2.3 萬減至約 1.4 萬，慳近 9,200。可見在可負擔範圍內盡量多還，對高息債務的效益極大。
常見問題
Why does paying more save more than the extra amount?
Because interest is charged on the outstanding principal each month. A higher payment cuts principal faster; as principal falls, the interest next month is smaller, so even more of the payment goes to principal — a compounding effect. The term shortens and total interest drops more than the extra dollars paid, especially on high-rate debt.
Why might the debt 'never be cleared'?
If the monthly payment is ≤ the monthly interest (balance x annual/12), the principal never drops — it may grow. Mathematically the payoff months formula breaks down; this tool flags it. Always pay above the interest to make progress.
How should I choose the extra payment?
Balance affordability against savings. Use this tool to see the trade-off at several levels, then pick the highest payment your budget can sustain — the interest saved is the 'return' on paying early. Keep an emergency fund and don't over-stretch.
Is this the same as the avalanche/snowball method?
No — this compares two overall monthly amounts on a single combined debt. Avalanche/snowball allocate a fixed total across multiple debts (by highest rate or smallest balance). Use this to size the total budget, then split it via avalanche/snowball across debts.
Why might the result differ from my lender's statement?
This model assumes a fixed annual rate, monthly accrual, on-time full payments and no new spending. Real loans may use daily accrual, flat (平息) vs APR conventions, plus fees/penalties and early-repayment charges. Treat it as a planning estimate; the lender's amortisation schedule is final.
相關工具
參考資料
內容審核：香港計算器財經團隊。計算邏輯與公式參考香港金融管理局（HKMA）及投資者及理財教育委員會（IFEC）之個人理財計算指引，結果僅供參考，實際以相關機構公佈為準。