Mortgage Calculator (Online) – Detailed Guide

This online mortgage calculator / loan calculator estimates monthly payments, total interest, total payment, and provides a full payment schedule. It also supports prepayment simulation and CSV export for deeper analysis.

1. What can this mortgage calculator do?

1.1 Multiple loan types

Commercial loan
Housing fund loan
Combo loan (commercial + fund)

1.2 Multiple payment methods

Equal payment (amortized): payment is roughly fixed each period
Equal principal: principal is fixed each period; total payment decreases over time
Interest-first: pay interest first and principal later (bank rules may vary)

1.3 Prepayment simulation (multiple entries)

Add one or more prepayment plans:

which period to prepay
amount
fee (if any)
mode:
- Reduce payment (keep term, reduce future monthly payment)
- Shorten term (keep payment as much as possible, finish earlier)

1.4 Detailed amortization schedule

For each period, the schedule shows:

principal
interest
payment
remaining principal

1.5 Export to CSV

Download the schedule as a CSV file to analyze in spreadsheets.

1.6 Local-only calculation (privacy)

All calculations run in your browser and are not uploaded.

2. How does mortgage calculation work? (Simple principle)

Mortgage payments are typically computed by spreading:

principal (the borrowed amount)
interest (based on the remaining principal)

across multiple periods.

The tool converts:

annual interest rate (%) → monthly interest rate (usually / 12)

Different methods mainly differ in how principal is allocated across periods. Prepayment reduces remaining principal earlier, which can reduce future interest.

3. Step-by-step tutorial

Step 1: Choose loan type

Select commercial / fund / combo.

Step 2: Fill in loan details

Enter:

loan amount
term (years)
annual rate (%)
payment method
start date

Step 3: Add prepayments (optional)

If you plan to prepay:

Click Add Prepayment
Set period, amount, fee
Choose reduce payment or shorten term

Step 4: Click Calculate

You will see:

monthly payment (or first payment)
total interest, total payment
interest saved (vs baseline without prepayment)
remaining principal
full amortization schedule

Step 5: Export CSV (optional)

Download the schedule for further comparison.

4. Feature & button explanation

4.1 Calculate

Runs the calculation using the current inputs.
Use it after changing any parameter.

4.2 Clear

Resets form, prepayments, and results.
Use it when comparing a different plan.

4.3 Add Prepayment

Adds a new prepayment entry.

4.4 Remove Prepayment

Deletes one prepayment entry.

4.5 Export CSV

Downloads the amortization schedule as CSV.

5. Common scenarios

5.1 Budget planning before buying a home

Compare monthly payment pressure across terms and rates.

5.2 Compare equal payment vs equal principal

See how payment trend differs and how total interest changes.

5.3 Evaluate prepayment strategies

Compare reduce payment vs shorten term to estimate interest savings and cash flow.

6. FAQ

6.1 Should I input annual rate or monthly rate?

Input annual rate (%). The tool converts it to monthly rate.

6.2 What is “prepayment period”?

It means the N-th payment period (usually monthly). For example, period 12 is roughly 12 months after start.

6.3 Why do results differ from the bank?

Banks may differ in:

day-count conventions
billing dates
exact prepayment handling

So this tool provides an estimate. Use the bank statement as the final reference.

6.4 How do I include prepayment fees?

Enter the fee in the prepayment entry; it will be included in totals.

7. Privacy & security

Local-only calculation; no uploads.
Avoid entering sensitive personal data on public/shared devices.

Summary: This online mortgage calculator supports multiple loan types and payment methods, provides prepayment simulation and CSV export, and helps you compare plans and estimate interest savings — all locally in your browser.

Mortgage Calculator

贷款信息

Commercial Loan

Prepayment