When extra payments may have the highest impact?
Key takeaways
04 · ideas- Month 1 extra payment saves 3x more than the same payment at month 200
- A $5,000 payment in year 1 saves ~$15,400 in interest
- The same $5,000 at month 300 saves only ~$1,200
- Refinancing before extra payments can multiply their impact
Basic level
The essentials · 1 min
Extra payments are most powerful when made early in the loan. Here's why: your mortgage balance is largest at the beginning, so every dollar you apply to principal in year 1 eliminates that dollar from a very long compound interest chain.
Think of it this way: $1,000 off your balance in month 1 means you avoid paying interest on that $1,000 for the next 29 years. $1,000 off in year 28 means you avoid interest for only 2 remaining years.
Simple rule: If you have money to put toward your mortgage, sooner is often better than later.
That said, "sooner" doesn't mean it may not be advisable to skip your emergency fund or pass up employer 401(k) match. Those priorities come first.
Intermediate level
How it applies · 2 min
The numbers behind timing
On a $200,000 mortgage at 7.5%, a $5,000 lump-sum payment:
| Payment timing | Interest saved | Months shortened |
|---|---|---|
| Month 1 (year 1) | ~$15,400 | ~14 months |
| Month 24 (year 2) | ~$13,800 | ~12 months |
| Month 60 (year 5) | ~$12,200 | ~10 months |
| Month 120 (year 10) | ~$8,100 | ~7 months |
| Month 180 (year 15) | ~$5,200 | ~4 months |
| Month 240 (year 20) | ~$3,100 | ~2.5 months |
| Month 300 (year 25) | ~$1,200 | ~1 month |
The dramatic dropoff after year 10 reflects the "crossover point" — by then you're past the high-interest early years.
The crossover point
In a 30-year mortgage, there's a point roughly at month 200-220 where more than 50% of each payment is going to principal rather than interest. Before that crossover, extra payments are extremely powerful. After it, they still help but the marginal impact is lower.
Biweekly payment strategy: Paying half your monthly payment every two weeks makes 26 half-payments = 13 full payments per year instead of 12. This one extra payment per year saves ~$30,000 on a typical mortgage and cuts 4–5 years off a 30-year loan — for essentially free.
Windfall strategy
If you receive a lump sum (bonus, tax refund, inheritance), the decision is:- Apply immediately to mortgage — an equivalent return at your loan rate (without market risk) at your mortgage rate (7.5%)
- Invest in market — expected ~10% nominal, ~7% real, but variable
- High-interest debt first — if you have credit cards at 20%, pay those first
If your mortgage rate > expected investment return after taxes → pay mortgage.
If your mortgage rate < expected investment return after taxes → invest.
At 7.5%, it's a close call — both are reasonable.
Advanced level
The math, step by step · 1 min
Mathematical proof of timing advantage
The present value of interest saved from a lump payment L made at month t of a n-month loan at monthly rate r:
As t \to 0 (early payment), this approaches L \cdot r \cdot n \cdot \frac{1}{1+r}, which is proportional to the full remaining term n.
As t \to n (late payment), interest saved approaches L \cdot r — just one period's interest.
The ratio: A payment in month 1 vs month 300 (on a 360-month loan) saves approximately (360/60) times more interest — roughly 6x the impact per dollar.
Optimal strategy if you have a fixed extra budget:- If you can only make extra payments for a limited time (e.g., 5 years until a major expense), concentrate all extra payments in the earliest possible months for maximum impact.
- If you expect your income to grow, start small now and increase annually — even 1% more per year compounds significantly over 30 years.