Compare mortgage plans

One loan. See how payments and interest evolve.

Fixed nominal rates · Monthly payments · JPY example · Excludes fees and other charges

Comparison inputs
50 million
Whole numbers, up to 10 billion.
First repayment month

Period 1 is this month; period 0 is the previous month. Dates do not change the calculation.

A Plan

Rate: 0–20%. Term: 1–600 whole months (up to 50 years).

B Plan

Rate: 0–20%. Term: 1–600 whole months (up to 50 years).

View a month
Repayment month

Period 168. Choose a month or click any chart; all views update together.

Monthly payment JPY

━ A · Equal payment┄ B · Equal principal
Monthly paymentFirst reversal at month 193: B is lower. Linear interpolation ≈ 192.2 months; 1 reversal(s).Selected 2040-08 · whole JPYA 153,092 JPYB 156,696 JPY060.5K121K181.5K2026-092044-032061-08Repayment month

Month 168 · A: 153,092.22 · B: 156,696.43 · A − B: -3,604.21

Cumulative interest difference A − B JPY

━ A − B
Cumulative interest difference A − BDifference A minus B: positive means A is higher; negative means B is higher.Selected 2040-08 · whole JPYA−B 383,186 JPY0380.8K761.7K1.1M2026-082044-022061-08Repayment month

Month 168 · A: 8,795,686.02 · B: 8,412,500.00 · A − B: 383,186.02

2 / 6 · Each view can show any metric.
A total interest14,298,732.34 JPY
B total interest13,156,250.00 JPY

Current comparison · Local calculation summary

Deterministic summary. No AI service is connected.

A − B is always the difference: a positive value means A is higher. A payment crossing only reverses the payment ranking; it does not establish which loan is best overall.

At the selected month, cumulative interest A − B is 383,186.02 JPY. Remaining principal A 33,076,193.09 / B 30,000,000.00 JPY.

Without fees: paid so far + remaining principal − original principal = interest paid. After payoff, payment and balance are zero; cumulative interest stays constant.

Repayment data · all months

JPY, displayed to 2 decimals; calculations are not rounded monthly. Month 0 is the opening position.

1 / 18
Same schedule as the charts · 24 months per page
MonthA PaymentA PrincipalA InterestA Cumulative interestA BalanceA Paid to dateB PaymentB PrincipalB InterestB Cumulative interestB BalanceB Paid to date
0 · 2026-080.000.000.000.0050,000,000.000.000.000.000.000.0050,000,000.000.00
1 · 2026-09153,092.2290,592.2262,500.0062,500.0049,909,407.78153,092.22181,547.62119,047.6262,500.0062,500.0049,880,952.38181,547.62
2 · 2026-10153,092.2290,705.4662,386.76124,886.7649,818,702.32306,184.44181,398.81119,047.6262,351.19124,851.1949,761,904.76362,946.43
3 · 2026-11153,092.2290,818.8462,273.38187,160.1449,727,883.48459,276.66181,250.00119,047.6262,202.38187,053.5749,642,857.14544,196.43
4 · 2026-12153,092.2290,932.3762,159.85249,319.9949,636,951.11612,368.88181,101.19119,047.6262,053.57249,107.1449,523,809.52725,297.62
5 · 2027-01153,092.2291,046.0362,046.19311,366.1849,545,905.08765,461.10180,952.38119,047.6261,904.76311,011.9049,404,761.90906,250.00
6 · 2027-02153,092.2291,159.8461,932.38373,298.5649,454,745.24918,553.32180,803.57119,047.6261,755.95372,767.8649,285,714.291,087,053.57
7 · 2027-03153,092.2291,273.7961,818.43435,116.9949,363,471.451,071,645.54180,654.76119,047.6261,607.14434,375.0049,166,666.671,267,708.33
8 · 2027-04153,092.2291,387.8861,704.34496,821.3349,272,083.571,224,737.76180,505.95119,047.6261,458.33495,833.3349,047,619.051,448,214.29
9 · 2027-05153,092.2291,502.1261,590.10558,411.4449,180,581.461,377,829.98180,357.14119,047.6261,309.52557,142.8648,928,571.431,628,571.43
10 · 2027-06153,092.2291,616.4961,475.73619,887.1649,088,964.971,530,922.20180,208.33119,047.6261,160.71618,303.5748,809,523.811,808,779.76
11 · 2027-07153,092.2291,731.0161,361.21681,248.3748,997,233.951,684,014.42180,059.52119,047.6261,011.90679,315.4848,690,476.191,988,839.29
12 · 2027-08153,092.2291,845.6861,246.54742,494.9148,905,388.271,837,106.64179,910.71119,047.6260,863.10740,178.5748,571,428.572,168,750.00
13 · 2027-09153,092.2291,960.4861,131.74803,626.6548,813,427.791,990,198.86179,761.90119,047.6260,714.29800,892.8648,452,380.952,348,511.90
14 · 2027-10153,092.2292,075.4461,016.78864,643.4348,721,352.362,143,291.08179,613.10119,047.6260,565.48861,458.3348,333,333.332,528,125.00
15 · 2027-11153,092.2292,190.5360,901.69925,545.1248,629,161.832,296,383.30179,464.29119,047.6260,416.67921,875.0048,214,285.712,707,589.29
16 · 2027-12153,092.2292,305.7760,786.45986,331.5848,536,856.062,449,475.52179,315.48119,047.6260,267.86982,142.8648,095,238.102,886,904.76
17 · 2028-01153,092.2292,421.1560,671.071,047,002.6548,444,434.912,602,567.74179,166.67119,047.6260,119.051,042,261.9047,976,190.483,066,071.43
18 · 2028-02153,092.2292,536.6860,555.541,107,558.1948,351,898.232,755,659.96179,017.86119,047.6259,970.241,102,232.1447,857,142.863,245,089.29
19 · 2028-03153,092.2292,652.3560,439.871,167,998.0648,259,245.892,908,752.18178,869.05119,047.6259,821.431,162,053.5747,738,095.243,423,958.33
20 · 2028-04153,092.2292,768.1660,324.061,228,322.1248,166,477.723,061,844.40178,720.24119,047.6259,672.621,221,726.1947,619,047.623,602,678.57
21 · 2028-05153,092.2292,884.1260,208.101,288,530.2248,073,593.603,214,936.62178,571.43119,047.6259,523.811,281,250.0047,500,000.003,781,250.00
22 · 2028-06153,092.2293,000.2360,091.991,348,622.2147,980,593.373,368,028.84178,422.62119,047.6259,375.001,340,625.0047,380,952.383,959,672.62
23 · 2028-07153,092.2293,116.4859,975.741,408,597.9547,887,476.893,521,121.06178,273.81119,047.6259,226.191,399,851.1947,261,904.764,137,946.43
Concepts

Equal payment keeps principal plus interest constant. Equal principal repays a constant share of principal, so payments decrease at a positive fixed rate. Interest is charged on the opening balance each month.

Japan Housing Finance Agency: repayment methods
Formulas and assumptions

Symbols

P
Original principal (JPY).
a
Nominal annual interest rate, e.g. 1.5%.
r
Monthly interest rate: r = a ÷ 12. For example, 1.5% ÷ 12 = 0.125% (= 0.00125).
n
Total number of monthly payments.
m
Current payment number, from 1 to n.
M
Fixed monthly payment for equal payment (JPY).
Mm
Payment in month m, including principal and interest (JPY).
Im
Interest paid in month m (JPY).
Cm
Principal repaid in month m (JPY).
Bm
Principal balance after payment m. B₀ = P; Bₘ₋₁ is the opening balance for month m.

Monthly payments

Equal payment (r > 0)

M = P × r ÷ [1 − (1 + r)−n]
Mm = M

Equal principal

Mm = P ÷ n + [P − P × (m − 1) ÷ n] × r

At zero interest, both methods have Mₘ = P ÷ n and Iₘ = 0.

Interest, principal and balance each month

Im = Bm−1 × r

Cm = Mm − Im

Bm = Bm−1 − Cm

Cumulative interest through month m is I₁ + I₂ + … + Iₘ; total interest uses m = n.

Model assumptions and display precision

  • Fixed nominal annual rate, monthly payments at the end of each period. No fees, taxes, prepayment or variable rates.
  • Calculations retain floating-point precision without bank-specific monthly rounding. The final payment clears the remaining principal; its amount may differ slightly from the ideal fixed payment.
  • Charts show whole JPY; tables show two decimal places. Display rounding does not change the calculation.
  • Equality tolerance is 0.00001 JPY. Crossings use straight-line interpolation between monthly samples; the interpolated month is not an actual repayment date.
Rate references and variable-rate boundaries

References checked 2026-09-05. Policy rates, prime rates and an actual mortgage offer are different. No live rates are fetched or inserted into this tool.

Five-year and 125% payment rules depend on the bank and contract. They do not cap the interest rate. Deferred unpaid interest is not automatically delinquency; this tool models neither such rules nor penalties.