背景
网上有很多在线版本的房贷计算器，但是想要不能对其结果进行自定义分析，所以就手动使用go语言写了一个房贷计算器，也可以通过C/C++/java编程语言将代码进行修改成自己的代码。
功能
- 支持等额本息/等额本金
- 支持计算每一期还款金额/利息/本金/还有多少本金未还/总的利息等
参考
- 等额本息理论: https://zhuanlan.zhihu.com/p/390581715
代码
package main
import (
"fmt"
"github.com/olekukonko/tablewriter"
"math"
"os"
"strconv"
)
// RepayStatEveryMonth 每个月还款统计
type RepayStatEveryMonth struct {
RepayAmount float64 // 每个月还款金额
RepayOfInterest float64 // 每个月还款的利息部分
RepayOfCorpus float64 // 每个月还款的本金部分
RemainCorpus float64 // 每个月还款之后还有多少本金未还
MonthId int // 第几个月份
}
// EqualityCorpus 等额本金
type EqualityCorpus struct {
InterestOfMonth float64 // 月利息
InterestOfYear float64 // 年利息
RepayMonths int // 还款月数
RepayCorpusEveryMonth float64 // 每个月还的本金数目
LoadAmount float64 // *款贷**金额
TotalRepayOfInterest float64 // 还款中利息部分
RepayDetail []RepayStatEveryMonth // 每个月还款细节
}
func (e *EqualityCorpus) calc() {
e.RepayCorpusEveryMonth = e.LoadAmount / float64(e.RepayMonths)
e.TotalRepayOfInterest = 0
for i := 1; i <= e.RepayMonths; i++ {
interest := (e.LoadAmount - float64(i-1)*e.RepayCorpusEveryMonth) * e.InterestOfMonth
e.TotalRepayOfInterest += interest
e.RepayDetail = append(e.RepayDetail, RepayStatEveryMonth{
RepayAmount: e.RepayCorpusEveryMonth + interest,
RepayOfInterest: interest,
RepayOfCorpus: e.RepayCorpusEveryMonth,
RemainCorpus: float64(e.RepayMonths-i) * e.RepayCorpusEveryMonth,
MonthId: i,
})
}
}
func NewEqualityCorpus(loadAmount, yearInterest float64, repayMonths int) *EqualityCorpus {
return &EqualityCorpus{
InterestOfMonth: yearInterest / 100.0 / 12.0,
InterestOfYear: yearInterest / 100.0,
RepayMonths: repayMonths,
LoadAmount: loadAmount,
TotalRepayOfInterest: 0,
RepayDetail: make([]RepayStatEveryMonth, 0),
}
}
// EqualityCorpusAndInterest 等额本息
type EqualityCorpusAndInterest struct {
InterestOfMonth float64 // 月利息
InterestOfYear float64 // 年利息
RepayMonths int // 还款月数
RepayAmountEveryMonth float64 // 每个月还款金额
LoadAmount float64 // *款贷**金额
TotalRepayOfInterest float64 // 还款中利息部分
RepayDetail []RepayStatEveryMonth // 每个月还款细节
}
func NewEqualityCorpusAndInterest(loadAmount, yearInterest float64, repayMonths int) *EqualityCorpusAndInterest {
return &EqualityCorpusAndInterest{
InterestOfMonth: yearInterest / 100.0 / 12.0,
InterestOfYear: yearInterest / 100.0,
RepayMonths: repayMonths,
RepayAmountEveryMonth: 0,
LoadAmount: loadAmount,
TotalRepayOfInterest: 0,
RepayDetail: make([]RepayStatEveryMonth, 0),
}
}
// 等额本息 参考: https://zhuanlan.zhihu.com/p/390581715
func (e *EqualityCorpusAndInterest) calc() {
// 计算每个月还款金额
X := func(A, R, n float64) float64 {
x1 := A * R * math.Pow(1+R, n)
x2 := math.Pow(1+R, n) - 1
return x1 / x2
}
// 每个月还款之后，还有多少本金未还
Q := func(A, R, x float64, k int) float64 {
x1 := math.Pow(1+R, float64(k))
x2 := 1 - x1
q := A*x1 + x*x2/R
return q
}
// 每个月还的利息
Rn := func(q, R float64) float64 {
return q * R
}
// 每个月还的本金
Cn := func(x, r float64) float64 {
return x - r
}
e.RepayAmountEveryMonth = X(e.LoadAmount, e.InterestOfMonth, float64(e.RepayMonths))
e.TotalRepayOfInterest = 0.0
for i := 1; i <= e.RepayMonths; i++ {
t := RepayStatEveryMonth{
RepayAmount: e.RepayAmountEveryMonth,
RepayOfInterest: 0,
RepayOfCorpus: 0,
RemainCorpus: Q(e.LoadAmount, e.InterestOfMonth, e.RepayAmountEveryMonth, i),
MonthId: i,
}
// caution: 这里是i-1,不是i，表示的是上个月的未还金额在一个月的时间内产生的利息
q := Q(e.LoadAmount, e.InterestOfMonth, e.RepayAmountEveryMonth, i-1)
t.RepayOfInterest = Rn(q, e.InterestOfMonth)
t.RepayOfCorpus = Cn(e.RepayAmountEveryMonth, t.RepayOfInterest)
e.RepayDetail = append(e.RepayDetail, t)
e.TotalRepayOfInterest += t.RepayOfInterest
}
}
func compareSummary(ec *EqualityCorpus, eci *EqualityCorpusAndInterest) {
table := tablewriter.NewWriter(os.Stdout)
table.SetHeader([]string{"还款方式", "期数", "*款贷**金额", "总利息", "利息/金额比例"})
data := [][]string{
{
"等额本息", strconv.FormatInt(int64(eci.RepayMonths), 10),
strconv.FormatInt(int64(eci.LoadAmount), 10),
strconv.FormatFloat(eci.TotalRepayOfInterest, 'f', 2, 64),
strconv.FormatFloat(100*eci.TotalRepayOfInterest/eci.LoadAmount, 'f', 2, 64) + "%",
},
{
"等额本金", strconv.FormatInt(int64(ec.RepayMonths), 10),
strconv.FormatInt(int64(ec.LoadAmount), 10),
strconv.FormatFloat(ec.TotalRepayOfInterest, 'f', 2, 64),
strconv.FormatFloat(100*ec.TotalRepayOfInterest/ec.LoadAmount, 'f', 2, 64) + "%",
},
}
for _, row := range data {
table.Append(row)
}
table.Render()
}
func compareDetail(ec *EqualityCorpus, eci *EqualityCorpusAndInterest, months int) {
if months > len(ec.RepayDetail) || months > len(eci.RepayDetail) {
fmt.Println("invalid param")
return
}
table := tablewriter.NewWriter(os.Stdout)
table.SetHeader([]string{
"月份",
"方式",
"还款金额",
"利息",
"本金",
"利息/金额比例",
"方式",
"还款金额",
"利息",
"本金",
"利息/金额比例",
})
for i := 0; i < months; i++ {
d := []string{
strconv.FormatInt(int64(i), 10),
"等额本息",
strconv.FormatFloat(eci.RepayDetail[i].RepayOfCorpus+eci.RepayDetail[i].RepayOfInterest, 'f', 2, 64),
strconv.FormatFloat(eci.RepayDetail[i].RepayOfInterest, 'f', 2, 64),
strconv.FormatFloat(eci.RepayDetail[i].RepayOfCorpus, 'f', 2, 64),
strconv.FormatFloat(eci.RepayDetail[i].RepayOfInterest*100/eci.RepayDetail[i].RepayOfCorpus, 'f', 2, 64) + "%",
"等额本金",
strconv.FormatFloat(ec.RepayDetail[i].RepayOfCorpus+ec.RepayDetail[i].RepayOfInterest, 'f', 2, 64),
strconv.FormatFloat(ec.RepayDetail[i].RepayOfInterest, 'f', 2, 64),
strconv.FormatFloat(ec.RepayDetail[i].RepayOfCorpus, 'f', 2, 64),
strconv.FormatFloat(ec.RepayDetail[i].RepayOfInterest*100/ec.RepayDetail[i].RepayOfCorpus, 'f', 2, 64) + "%",
}
table.Append(d)
}
table.Render()
}
func main() {
loadAmount, yearInterest, months := float64(1000000), 4.75, 60
x := NewEqualityCorpus(loadAmount, yearInterest, months)
x.calc()
y := NewEqualityCorpusAndInterest(loadAmount, yearInterest, months)
y.calc()
compareSummary(x, y)
compareDetail(x, y, months)
}
执行结果
+----------+------+----------+-----------+---------------+
| 还款方式 | 期数 | *款贷**金额 | 总利息 | 利息/金额比例 |
+----------+------+----------+-----------+---------------+
| 等额本息 | 60 | 1000000 | 125414.72 | 12.54% |
| 等额本金 | 60 | 1000000 | 120729.17 | 12.07% |
+----------+------+----------+-----------+---------------+
+------+----------+----------+---------+----------+---------------+----------+----------+---------+----------+---------------+
| 月份 | 方式 | 还款金额 | 利息 | 本金 | 利息/金额比例 | 方式 | 还款金额 | 利息 | 本金 | 利息/金额比例 |
+------+----------+----------+---------+----------+---------------+----------+----------+---------+----------+---------------+
| 0 | 等额本息 | 18756.91 | 3958.33 | 14798.58 | 26.75% | 等额本金 | 20625.00 | 3958.33 | 16666.67 | 23.75% |
| 1 | 等额本息 | 18756.91 | 3899.76 | 14857.16 | 26.25% | 等额本金 | 20559.03 | 3892.36 | 16666.67 | 23.35% |
| 2 | 等额本息 | 18756.91 | 3840.95 | 14915.97 | 25.75% | 等额本金 | 20493.06 | 3826.39 | 16666.67 | 22.96% |
| 3 | 等额本息 | 18756.91 | 3781.90 | 14975.01 | 25.25% | 等额本金 | 20427.08 | 3760.42 | 16666.67 | 22.56% |
| 4 | 等额本息 | 18756.91 | 3722.63 | 15034.28 | 24.76% | 等额本金 | 20361.11 | 3694.44 | 16666.67 | 22.17% |
| 5 | 等额本息 | 18756.91 | 3663.12 | 15093.80 | 24.27% | 等额本金 | 20295.14 | 3628.47 | 16666.67 | 21.77% |
| 6 | 等额本息 | 18756.91 | 3603.37 | 15153.54 | 23.78% | 等额本金 | 20229.17 | 3562.50 | 16666.67 | 21.38% |
| 7 | 等额本息 | 18756.91 | 3543.39 | 15213.52 | 23.29% | 等额本金 | 20163.19 | 3496.53 | 16666.67 | 20.98% |
| 8 | 等额本息 | 18756.91 | 3483.17 | 15273.74 | 22.80% | 等额本金 | 20097.22 | 3430.56 | 16666.67 | 20.58% |
| 9 | 等额本息 | 18756.91 | 3422.71 | 15334.20 | 22.32% | 等额本金 | 20031.25 | 3364.58 | 16666.67 | 20.19% |
| 10 | 等额本息 | 18756.91 | 3362.01 | 15394.90 | 21.84% | 等额本金 | 19965.28 | 3298.61 | 16666.67 | 19.79% |
| 11 | 等额本息 | 18756.91 | 3301.07 | 15455.84 | 21.36% | 等额本金 | 19899.31 | 3232.64 | 16666.67 | 19.40% |
| 12 | 等额本息 | 18756.91 | 3239.89 | 15517.02 | 20.88% | 等额本金 | 19833.33 | 3166.67 | 16666.67 | 19.00% |
| 13 | 等额本息 | 18756.91 | 3178.47 | 15578.44 | 20.40% | 等额本金 | 19767.36 | 3100.69 | 16666.67 | 18.60% |
| 14 | 等额本息 | 18756.91 | 3116.81 | 15640.10 | 19.93% | 等额本金 | 19701.39 | 3034.72 | 16666.67 | 18.21% |
| 15 | 等额本息 | 18756.91 | 3054.90 | 15702.01 | 19.46% | 等额本金 | 19635.42 | 2968.75 | 16666.67 | 17.81% |
| 16 | 等额本息 | 18756.91 | 2992.74 | 15764.17 | 18.98% | 等额本金 | 19569.44 | 2902.78 | 16666.67 | 17.42% |
| 17 | 等额本息 | 18756.91 | 2930.35 | 15826.57 | 18.52% | 等额本金 | 19503.47 | 2836.81 | 16666.67 | 17.02% |
| 18 | 等额本息 | 18756.91 | 2867.70 | 15889.21 | 18.05% | 等额本金 | 19437.50 | 2770.83 | 16666.67 | 16.62% |
| 19 | 等额本息 | 18756.91 | 2804.80 | 15952.11 | 17.58% | 等额本金 | 19371.53 | 2704.86 | 16666.67 | 16.23% |
| 20 | 等额本息 | 18756.91 | 2741.66 | 16015.25 | 17.12% | 等额本金 | 19305.56 | 2638.89 | 16666.67 | 15.83% |
| 21 | 等额本息 | 18756.91 | 2678.27 | 16078.65 | 16.66% | 等额本金 | 19239.58 | 2572.92 | 16666.67 | 15.44% |
| 22 | 等额本息 | 18756.91 | 2614.62 | 16142.29 | 16.20% | 等额本金 | 19173.61 | 2506.94 | 16666.67 | 15.04% |
| 23 | 等额本息 | 18756.91 | 2550.72 | 16206.19 | 15.74% | 等额本金 | 19107.64 | 2440.97 | 16666.67 | 14.65% |
| 24 | 等额本息 | 18756.91 | 2486.58 | 16270.34 | 15.28% | 等额本金 | 19041.67 | 2375.00 | 16666.67 | 14.25% |
| 25 | 等额本息 | 18756.91 | 2422.17 | 16334.74 | 14.83% | 等额本金 | 18975.69 | 2309.03 | 16666.67 | 13.85% |
| 26 | 等额本息 | 18756.91 | 2357.51 | 16399.40 | 14.38% | 等额本金 | 18909.72 | 2243.06 | 16666.67 | 13.46% |
| 27 | 等额本息 | 18756.91 | 2292.60 | 16464.31 | 13.92% | 等额本金 | 18843.75 | 2177.08 | 16666.67 | 13.06% |
| 28 | 等额本息 | 18756.91 | 2227.43 | 16529.48 | 13.48% | 等额本金 | 18777.78 | 2111.11 | 16666.67 | 12.67% |
| 29 | 等额本息 | 18756.91 | 2162.00 | 16594.91 | 13.03% | 等额本金 | 18711.81 | 2045.14 | 16666.67 | 12.27% |
| 30 | 等额本息 | 18756.91 | 2096.31 | 16660.60 | 12.58% | 等额本金 | 18645.83 | 1979.17 | 16666.67 | 11.87% |
| 31 | 等额本息 | 18756.91 | 2030.36 | 16726.55 | 12.14% | 等额本金 | 18579.86 | 1913.19 | 16666.67 | 11.48% |
| 32 | 等额本息 | 18756.91 | 1964.15 | 16792.76 | 11.70% | 等额本金 | 18513.89 | 1847.22 | 16666.67 | 11.08% |
| 33 | 等额本息 | 18756.91 | 1897.68 | 16859.23 | 11.26% | 等额本金 | 18447.92 | 1781.25 | 16666.67 | 10.69% |
| 34 | 等额本息 | 18756.91 | 1830.95 | 16925.96 | 10.82% | 等额本金 | 18381.94 | 1715.28 | 16666.67 | 10.29% |
| 35 | 等额本息 | 18756.91 | 1763.95 | 16992.96 | 10.38% | 等额本金 | 18315.97 | 1649.31 | 16666.67 | 9.90% |
| 36 | 等额本息 | 18756.91 | 1696.68 | 17060.23 | 9.95% | 等额本金 | 18250.00 | 1583.33 | 16666.67 | 9.50% |
| 37 | 等额本息 | 18756.91 | 1629.15 | 17127.76 | 9.51% | 等额本金 | 18184.03 | 1517.36 | 16666.67 | 9.10% |
| 38 | 等额本息 | 18756.91 | 1561.36 | 17195.55 | 9.08% | 等额本金 | 18118.06 | 1451.39 | 16666.67 | 8.71% |
| 39 | 等额本息 | 18756.91 | 1493.29 | 17263.62 | 8.65% | 等额本金 | 18052.08 | 1385.42 | 16666.67 | 8.31% |
| 40 | 等额本息 | 18756.91 | 1424.96 | 17331.96 | 8.22% | 等额本金 | 17986.11 | 1319.44 | 16666.67 | 7.92% |
| 41 | 等额本息 | 18756.91 | 1356.35 | 17400.56 | 7.79% | 等额本金 | 17920.14 | 1253.47 | 16666.67 | 7.52% |
| 42 | 等额本息 | 18756.91 | 1287.47 | 17469.44 | 7.37% | 等额本金 | 17854.17 | 1187.50 | 16666.67 | 7.12% |
| 43 | 等额本息 | 18756.91 | 1218.32 | 17538.59 | 6.95% | 等额本金 | 17788.19 | 1121.53 | 16666.67 | 6.73% |
| 44 | 等额本息 | 18756.91 | 1148.90 | 17608.01 | 6.52% | 等额本金 | 17722.22 | 1055.56 | 16666.67 | 6.33% |
| 45 | 等额本息 | 18756.91 | 1079.20 | 17677.71 | 6.10% | 等额本金 | 17656.25 | 989.58 | 16666.67 | 5.94% |
| 46 | 等额本息 | 18756.91 | 1009.23 | 17747.68 | 5.69% | 等额本金 | 17590.28 | 923.61 | 16666.67 | 5.54% |
| 47 | 等额本息 | 18756.91 | 938.98 | 17817.94 | 5.27% | 等额本金 | 17524.31 | 857.64 | 16666.67 | 5.15% |
| 48 | 等额本息 | 18756.91 | 868.45 | 17888.46 | 4.85% | 等额本金 | 17458.33 | 791.67 | 16666.67 | 4.75% |
| 49 | 等额本息 | 18756.91 | 797.64 | 17959.27 | 4.44% | 等额本金 | 17392.36 | 725.69 | 16666.67 | 4.35% |
| 50 | 等额本息 | 18756.91 | 726.55 | 18030.36 | 4.03% | 等额本金 | 17326.39 | 659.72 | 16666.67 | 3.96% |
| 51 | 等额本息 | 18756.91 | 655.18 | 18101.73 | 3.62% | 等额本金 | 17260.42 | 593.75 | 16666.67 | 3.56% |
| 52 | 等额本息 | 18756.91 | 583.53 | 18173.39 | 3.21% | 等额本金 | 17194.44 | 527.78 | 16666.67 | 3.17% |
| 53 | 等额本息 | 18756.91 | 511.59 | 18245.32 | 2.80% | 等额本金 | 17128.47 | 461.81 | 16666.67 | 2.77% |
| 54 | 等额本息 | 18756.91 | 439.37 | 18317.54 | 2.40% | 等额本金 | 17062.50 | 395.83 | 16666.67 | 2.37% |
| 55 | 等额本息 | 18756.91 | 366.86 | 18390.05 | 1.99% | 等额本金 | 16996.53 | 329.86 | 16666.67 | 1.98% |
| 56 | 等额本息 | 18756.91 | 294.07 | 18462.84 | 1.59% | 等额本金 | 16930.56 | 263.89 | 16666.67 | 1.58% |
| 57 | 等额本息 | 18756.91 | 220.99 | 18535.93 | 1.19% | 等额本金 | 16864.58 | 197.92 | 16666.67 | 1.19% |
| 58 | 等额本息 | 18756.91 | 147.62 | 18609.30 | 0.79% | 等额本金 | 16798.61 | 131.94 | 16666.67 | 0.79% |
| 59 | 等额本息 | 18756.91 | 73.95 | 18682.96 | 0.40% | 等额本金 | 16732.64 | 65.97 | 16666.67 | 0.40% |
+------+----------+----------+---------+----------+---------------+----------+----------+---------+----------+---------------+
Process finished with the exit code 0
校验
- 可以通过现有的在线房贷计算器进行校验：http://daikuan.jsq886.com