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Interest & Installment Calculator
Work out loan installments and interest with flat, effective (reducing balance) or tiered rates, then export the schedule to CSV, Excel or PDF.
Loan
% / year
Interest basis
Summary
Monthly installment
19,566.15
60 installments
- Total interest
- 173,968.87
- Total paid
- 1,173,968.87
- Effective rate (EIR)
- 6.5% / yr
- Flat-rate equivalent
- 3.479% / yr
Principal 85.2%Interest 14.8%
Installment schedule
| # | Date | Rate % | Installment | Principal | Interest | Balance |
|---|---|---|---|---|---|---|
| 1 | — | 6.5 | 19,566.15 | 14,149.48 | 5,416.67 | 985,850.52 |
| 2 | — | 6.5 | 19,566.15 | 14,226.13 | 5,340.02 | 971,624.39 |
| 3 | — | 6.5 | 19,566.15 | 14,303.18 | 5,262.97 | 957,321.21 |
| 4 | — | 6.5 | 19,566.15 | 14,380.66 | 5,185.49 | 942,940.55 |
| 5 | — | 6.5 | 19,566.15 | 14,458.56 | 5,107.59 | 928,481.99 |
| 6 | — | 6.5 | 19,566.15 | 14,536.87 | 5,029.28 | 913,945.12 |
| 7 | — | 6.5 | 19,566.15 | 14,615.61 | 4,950.54 | 899,329.51 |
| 8 | — | 6.5 | 19,566.15 | 14,694.78 | 4,871.37 | 884,634.73 |
| 9 | — | 6.5 | 19,566.15 | 14,774.38 | 4,791.77 | 869,860.35 |
| 10 | — | 6.5 | 19,566.15 | 14,854.41 | 4,711.74 | 855,005.94 |
| 11 | — | 6.5 | 19,566.15 | 14,934.87 | 4,631.28 | 840,071.07 |
| 12 | — | 6.5 | 19,566.15 | 15,015.77 | 4,550.38 | 825,055.30 |
| 13 | — | 6.5 | 19,566.15 | 15,097.10 | 4,469.05 | 809,958.20 |
| 14 | — | 6.5 | 19,566.15 | 15,178.88 | 4,387.27 | 794,779.32 |
| 15 | — | 6.5 | 19,566.15 | 15,261.10 | 4,305.05 | 779,518.22 |
| 16 | — | 6.5 | 19,566.15 | 15,343.76 | 4,222.39 | 764,174.46 |
| 17 | — | 6.5 | 19,566.15 | 15,426.87 | 4,139.28 | 748,747.59 |
| 18 | — | 6.5 | 19,566.15 | 15,510.43 | 4,055.72 | 733,237.16 |
| 19 | — | 6.5 | 19,566.15 | 15,594.45 | 3,971.70 | 717,642.71 |
| 20 | — | 6.5 | 19,566.15 | 15,678.92 | 3,887.23 | 701,963.79 |
| 21 | — | 6.5 | 19,566.15 | 15,763.85 | 3,802.30 | 686,199.94 |
| 22 | — | 6.5 | 19,566.15 | 15,849.23 | 3,716.92 | 670,350.71 |
| 23 | — | 6.5 | 19,566.15 | 15,935.08 | 3,631.07 | 654,415.63 |
| 24 | — | 6.5 | 19,566.15 | 16,021.40 | 3,544.75 | 638,394.23 |
| 25 | — | 6.5 | 19,566.15 | 16,108.18 | 3,457.97 | 622,286.05 |
| 26 | — | 6.5 | 19,566.15 | 16,195.43 | 3,370.72 | 606,090.62 |
| 27 | — | 6.5 | 19,566.15 | 16,283.16 | 3,282.99 | 589,807.46 |
| 28 | — | 6.5 | 19,566.15 | 16,371.36 | 3,194.79 | 573,436.10 |
| 29 | — | 6.5 | 19,566.15 | 16,460.04 | 3,106.11 | 556,976.06 |
| 30 | — | 6.5 | 19,566.15 | 16,549.20 | 3,016.95 | 540,426.86 |
| 31 | — | 6.5 | 19,566.15 | 16,638.84 | 2,927.31 | 523,788.02 |
| 32 | — | 6.5 | 19,566.15 | 16,728.96 | 2,837.19 | 507,059.06 |
| 33 | — | 6.5 | 19,566.15 | 16,819.58 | 2,746.57 | 490,239.48 |
| 34 | — | 6.5 | 19,566.15 | 16,910.69 | 2,655.46 | 473,328.79 |
| 35 | — | 6.5 | 19,566.15 | 17,002.29 | 2,563.86 | 456,326.50 |
| 36 | — | 6.5 | 19,566.15 | 17,094.38 | 2,471.77 | 439,232.12 |
| 37 | — | 6.5 | 19,566.15 | 17,186.98 | 2,379.17 | 422,045.14 |
| 38 | — | 6.5 | 19,566.15 | 17,280.07 | 2,286.08 | 404,765.07 |
| 39 | — | 6.5 | 19,566.15 | 17,373.67 | 2,192.48 | 387,391.40 |
| 40 | — | 6.5 | 19,566.15 | 17,467.78 | 2,098.37 | 369,923.62 |
| 41 | — | 6.5 | 19,566.15 | 17,562.40 | 2,003.75 | 352,361.22 |
| 42 | — | 6.5 | 19,566.15 | 17,657.53 | 1,908.62 | 334,703.69 |
| 43 | — | 6.5 | 19,566.15 | 17,753.17 | 1,812.98 | 316,950.52 |
| 44 | — | 6.5 | 19,566.15 | 17,849.33 | 1,716.82 | 299,101.19 |
| 45 | — | 6.5 | 19,566.15 | 17,946.02 | 1,620.13 | 281,155.17 |
| 46 | — | 6.5 | 19,566.15 | 18,043.23 | 1,522.92 | 263,111.94 |
| 47 | — | 6.5 | 19,566.15 | 18,140.96 | 1,425.19 | 244,970.98 |
| 48 | — | 6.5 | 19,566.15 | 18,239.22 | 1,326.93 | 226,731.76 |
| 49 | — | 6.5 | 19,566.15 | 18,338.02 | 1,228.13 | 208,393.74 |
| 50 | — | 6.5 | 19,566.15 | 18,437.35 | 1,128.80 | 189,956.39 |
| 51 | — | 6.5 | 19,566.15 | 18,537.22 | 1,028.93 | 171,419.17 |
| 52 | — | 6.5 | 19,566.15 | 18,637.63 | 928.52 | 152,781.54 |
| 53 | — | 6.5 | 19,566.15 | 18,738.58 | 827.57 | 134,042.96 |
| 54 | — | 6.5 | 19,566.15 | 18,840.08 | 726.07 | 115,202.88 |
| 55 | — | 6.5 | 19,566.15 | 18,942.13 | 624.02 | 96,260.75 |
| 56 | — | 6.5 | 19,566.15 | 19,044.74 | 521.41 | 77,216.01 |
| 57 | — | 6.5 | 19,566.15 | 19,147.90 | 418.25 | 58,068.11 |
| 58 | — | 6.5 | 19,566.15 | 19,251.61 | 314.54 | 38,816.50 |
| 59 | — | 6.5 | 19,566.15 | 19,355.89 | 210.26 | 19,460.61 |
| 60 | — | 6.5 | 19,566.02 | 19,460.61 | 105.41 | 0.00 |
Flat, effective and tiered rates
- Flat rate (ดอกเบี้ยคงที่) charges interest on the original amount for the whole term: interest = amount × rate × years, split evenly over the installments. Common for car and hire-purchase loans. Because you keep paying interest on money already repaid, the real cost is about double the flat rate — see the effective rate (EIR) in the summary.
- Effective rate (ดอกเบี้ยลดต้นลดดอก) charges interest only on the remaining balance each month, with an equal installment. Used by home loans, personal loans and most bank lending.
- Tiered rate (ดอกเบี้ยขั้นบันได) is a reducing-balance loan whose rate steps up over time, e.g. 2.9% in year 1, 3.5% in year 2, then MRR − 1% for the rest. The installment is recalculated at each step, unless you set a fixed installment. Banks often advertise the average rate for the first 3 years, which the summary shows too.
- Banks in Thailand charge reducing-balance interest daily (rate × days ÷ 365). Pick Daily as the interest basis to match a bank statement; months with 31 days cost slightly more.
- A fixed installment that is higher than needed pays the loan off early; one that is too low leaves a lump sum in the last installment.
Exports
- CSV and Excel download the full monthly schedule and summary. PDF opens your browser's print dialog — choose “Save as PDF”.
- Results are estimates; your lender's rounding, fees and payment dates may differ slightly. Everything is calculated in your browser.