Equal Payment vs Equal Principal: Which Repayment Method Costs Less?

Borrow $300,000 at 6.5% a year for 30 years and the lender may offer two schedules. With equal payments you pay $1,896.20 every month and $382,636.71 in interest over the life of the loan. With equal principal your first payment is $2,458.33, it falls a little every month down to $839.05, and the total interest is $293,313.66 — $89,323.05 less. Same amount, same rate, same term.

Both methods charge interest only on the balance you still owe, so neither one is a "flat rate" trick. The difference is how fast you repay the principal. Equal payments keep the total payment constant, so the early payments are mostly interest. Equal principal repays the same slice of principal every month, so the balance — and with it the interest — falls faster.

Loan Calculator shows both methods side by side for any loan, with the trade-off spelled out in one line: how much more you pay at the start, and how much interest you save in total.

What should you compare?

The cheaper method on paper is not always the right one for your budget. Put these side by side:

• First payment — the highest payment of an equal-principal loan comes on day one. Make sure you can carry it comfortably.
• Total interest — what the loan costs over its whole life.
• Balance after a few years — what you would still owe if you sell, refinance or repay early.
• Rate-rise risk — on a floating-rate loan, how high the payment could go if rates climb.

Equal payment vs equal principal at a glance

All figures are for $300,000 at 6.5% a year over 360 months.

The equal-principal payment starts $562.13 higher and drops below the equal payment only in month 126, more than ten years in.

1. Equal payments: the same amount every month

Best for: a predictable budget, long terms, and borrowers whose income is tightest in the first years of the loan.

The payment is fixed so that, after the last one, the balance is exactly zero:

r = annual rate ÷ 12 = 6.5% ÷ 12
Payment = P × r ÷ (1 − (1 + r)^−n)
        = 300,000 × r ÷ (1 − (1 + r)^−360) = $1,896.20

Inside that fixed amount, interest comes first. In month 1 the interest is $1,625.00, so only $271.20 repays principal. The split shifts slowly in your favor, and it takes until month 233 for principal to overtake interest. The amortization schedule guide walks through that month by month.

The last payment ($1,900.91 here) differs by a few dollars because every month is rounded to the cent and the final row settles the difference.

2. Equal principal: high at first, lower every month

Best for: borrowers who can afford a larger payment now, expect their income to fall later (for example at retirement), or simply want to pay less interest.

The principal is split evenly across the term, and interest is added on the balance still owed:

Principal part  = P ÷ n = 300,000 ÷ 360 = $833.33
Interest, month 1 = 300,000 × 6.5% ÷ 12 = $1,625.00
First payment   = 833.33 + 1,625.00 = $2,458.33

Each month the balance drops by the same $833.33, so the interest drops by about $4.51 and so does the payment: $2,408.68 in month 12, $2,192.01 in month 60, $1,650.35 in month 180 and finally $839.05. That last payment repays $834.53 of principal rather than $833.33, because it also clears what rounding left behind.

The saving is real, but it comes from paying more earlier. In year 1 an equal-principal borrower pays $29,202.05, which is $6,447.65 more than with equal payments. Counted from day one, the equal-principal borrower has paid more cash in total for the first 250 months. From month 251 on the running total is lower, and it ends $89,323.05 lower.

3. The real trade-off: cash flow now vs interest later

Best for: deciding with your own numbers instead of a rule of thumb.

Think of equal principal as equal payments plus a built-in prepayment. After ten years, the equal-principal borrower has paid $262,770.56 against $227,544.00, and owes $200,000.40 against $254,329.14. The extra cash went straight into principal, which is why less interest follows.

How much that matters depends on the size and length of the loan:

On a short car loan the gap is small, and the higher start may not be worth the squeeze. On a 30-year mortgage the gap is large enough to plan around.

Rates matter too. If a floating rate rose 2 percentage points, equal payments would climb to about $2,307 and cost $147,790.18 more interest. Equal principal would start at $2,958.33 but add only $90,250.37 — the balance is lower, so there is less to charge the higher rate on.

4. How to compare both methods in Loan Calculator

Best for: checking a real quote in about a minute, with or without a connection.

1. Enter the Loan amount, the Annual interest rate (%/year) and the Term. Under Interest method, keep Equal payment selected.
2. Tap Calculate. The result shows the Monthly payment, $1,896.20 in our example.
3. Scroll to Interest methods compared. It lists the first payment and total interest for equal payments, equal principal and flat rate, then sums up: "Equal principal: first payment $562.13 higher than equal payments, but $89,323.05 less interest in total."
4. Switch Interest method to Equal principal and tap Calculate again. The headline becomes First payment, and a note reads "Payments fall every month: highest $2,458.33, last $839.05."
5. Open Amortization schedule and switch between Equal payment and Equal principal at the top to compare row by row. On the Charts tab, the equal-principal balance falls in a straight line while the equal-payment balance curves.
6. Check the If interest rates rise card for the highest payment and extra interest at +1, +2 and +3 percentage points.

The card values are shortened (for example "2.46K") to fit the screen. The schedule shows every amount in full.

Which method should you choose?

Often the lender decides which method applies. If you are offered a choice:

FAQ

Is equal principal always cheaper than equal payments?

At the same rate and term, yes — equal principal repays principal faster, so less interest accrues. The trade-off is a higher payment at the start. For our $300,000 example that is $562.13 more in month 1 for $89,323.05 less interest overall.

Why does the equal-principal payment fall every month?

The principal part is fixed ($833.33 here), but the balance drops by that amount each month, so the interest on it drops by about $4.51 each time. Payment = fixed principal + shrinking interest.

Can I get the equal-principal savings with an equal-payment loan?

You can get close by paying extra toward principal, because that is what equal principal does automatically. Check your contract for prepayment fees first, then model the effect with the Prepayment simulator (part of Pro, or unlocked for 24 hours with 3 credits).

Does the method change my first-month interest?

No. In month 1 both methods charge interest on the full amount: $1,625.00 here. The difference starts from month 2, because equal principal has already repaid $833.33 of principal rather than $271.20.

Which method does the app use by default?

Equal payment is selected by default. Your choice is shown in the note under the results, for example "Worked out as: Equal principal (declining payments) · annual rate ÷ 12".