BA II Plus Amortization: Split Every Payment into Principal and Interest

In this tutorial

• How the AMORT worksheet is organized: P1, P2, BAL, PRN, INT
• Step 1: solve the payment with TVM first
• Example 1: first-year split on a $300,000 mortgage
• Example 2: a full car-loan schedule and total interest
• Reading BAL, PRN and INT the right way (signs included)
• Payoff balances, cumulative totals and common mistakes

The six fields of the AMORT worksheet

Press [2nd] then [AMORT] (above the [PV] key) to open the worksheet. It reuses the loan values you just solved in TVM — you do not re-enter the rate or the payment. The fields are:

• P1 — the first payment number of the range you want.
• P2 — the last payment number of the range.
• BAL — the balance remaining after the P2 payment (computed automatically).
• PRN — total principal paid between P1 and P2.
• INT — total interest paid between P1 and P2.

To answer "what is the split of payment 47?", set P1 = 47 and P2 = 47. To answer "what happened in year 3?", set P1 = 25 and P2 = 36 for monthly payments.

Step 0: solve the payment with TVM

AMORT works from the TVM registers, so compute the payment first. Use the setup from the BA II Plus basics tutorial: P/Y = 1, decimals at 4 or 9, and enter the monthly rate as I/Y (annual rate ÷ 12) with N in months.

Example 1: first-year split on a $300,000, 30-year mortgage at 6%

Step 1 — find the payment.

1. Press [2nd] then [CLR TVM].
2. Enter 360 (30 × 12), press [N].
3. Enter 6 ÷ 12 = 0.5 — type 0.5, press [I/Y].
4. Enter 300000, press [PV].
5. Leave FV at 0.
6. Press [CPT] then [PMT] — the display shows −1,798.65.

Step 2 — open AMORT and set the first year.

7. Press [2nd] then [AMORT].
8. At P1, enter 1, press [ENTER].
9. Scroll down to P2, enter 12, press [ENTER].
10. Scroll down to BAL — 296,337.74 is still owed after payment 12.
11. Scroll down to PRN — −3,662.26 of principal was paid in year 1.
12. Scroll down to INT — −17,921.54 of interest was paid in year 1.

Sanity check: 12 payments of $1,798.65 total $21,583.80, and $3,662.26 + $17,921.54 = $21,583.80. Exactly right. Notice the first year is almost 83% interest — that is normal for a long mortgage and the reason refinancing questions feel like pure interest math.

Example 2: a full car-loan schedule and total interest

A $20,000 car loan at 7% annual interest, 5 years, paid monthly. What is the payment, and what is the total interest over the life of the loan?

Step 1 — payment.

1. Press [2nd] then [CLR TVM].
2. Enter 60 (5 × 12), press [N].
3. Enter 7 ÷ 12 = 0.583333, press [I/Y].
4. Enter 20000, press [PV].
5. Press [CPT] then [PMT] — −395.95.

Step 2 — total interest over the whole loan.

6. Press [2nd] then [AMORT].
7. At P1, enter 1, press [ENTER].
8. At P2, enter 60, press [ENTER].
9. Scroll down — BAL shows 0.00 (the loan is fully paid).
10. Scroll down — PRN shows −20,000 (all principal repaid).
11. Scroll down — INT shows −3,757.00, the total interest.

Cross-check: 60 payments × $395.95 = $23,757, minus the $20,000 principal = $3,757 in interest. The worksheet agrees to the penny.

Building a year-by-year amortization schedule

You can page through the whole loan by repeating the same steps with a moving window: set P1 = 1, P2 = 12 for year 1; then P1 = 13, P2 = 24 for year 2; and so on. Record BAL after each block — that is your year-end balance column. The pattern is: each year's P1 is the previous P2 plus 1. On the exam, the year-end balance after payment 12 is often exactly what a question asks for; you do not need to write out all 360 rows.

Reading the signs on BAL, PRN and INT

• BAL is always shown positive — it is the outstanding balance, not a cash flow.
• PRN and INT carry the sign of the payment you solved in TVM. Because PMT was negative (money paid out), the principal and interest amounts also display negative. Report them as positive magnitudes: "the principal portion was $3,662.26".
• If you solved PMT as positive by entering PV positive, AMORT mirrors that sign — the split is the same, only the sign flips.

Payoff balance without the AMORT menu

When you only need the remaining balance (say, after the 85th payment), the fastest route is still AMORT with P1 = P2 = 85 and reading BAL. The basics tutorial also shows Jim Maher's Method A — recompute PV with N set to the remaining payments — which is a great second check. Both answers must match; if they do not, an entry in TVM drifted.

Common mistakes and error traps

• Forgetting to solve PMT first. AMORT reads whatever is in the TVM registers; stale values give nonsense splits.
• P1 greater than P2. The range is invalid — re-enter the smaller number at P1.
• Mixing periods. If N is in months, P1/P2 are payment numbers, not years.
• Trusting the sign. Report INT and PRN as magnitudes; the negative sign is just the payment direction.
• Rounding the payment too early. Keep the calculator's stored value; if you type $1,798.65 back in, the balance will be off by a few cents that grow with every period.

Related tutorials

Amortization is TVM applied period by period, the same engine behind bond YTM calculations. When a problem quotes actual payment dates, the Date worksheet helps you count days and find maturity dates. And if the worksheet throws an error, check the reset and error-code guide before re-entering everything. For the full TVM foundation, revisit the basics and advanced functions tutorials.

References

• Texas Instruments — BA II PLUS Guidebook (official user manual)
• Texas Instruments — BA II PLUS PROFESSIONAL Calculator Guide
• AEA — How to Use a BA II Plus Financial Calculator
• Eastern Illinois University — Using the Texas Instruments BAII Plus