Estimated mortgage principal

Calculate estimated mortgage principal using the values and assumptions you provide.

Your inputs stay in your browser. Displayed results are rounded to a maximum of 12 significant digits.

Method and assumptions

Method version 1.0.0 · Updated October 18, 2026

Calculate

Formula: Principal = payment × [1 − (1 + r)⁻ⁿ] / r

Calculate estimated mortgage principal using the values and assumptions you provide.

Results depend on the assumptions entered; verify professional or safety-critical decisions independently.

These short examples use the same inputs and core calculation as this tool. Adapt validation and formatting to your application.

JavaScript

const budget = 1200, rate = 0.04 / 12, months = 300;
console.log(budget * (1 - (1 + rate) ** -months) / rate); // estimated principal

TypeScript

const budget = 1200, rate = 0.04 / 12, months = 300;
const principal: number = budget * (1 - (1 + rate) ** -months) / rate;
console.log(principal);

Python

budget, rate, months = 1200, 0.04 / 12, 300
print(budget * (1 - (1 + rate) ** -months) / rate)

Java

double p = 1200 * (1 - Math.pow(1 + 0.04 / 12, -300)) / (0.04 / 12);
System.out.println(p);

double p = 1200 * (1 - Math.Pow(1 + 0.04 / 12, -300)) / (0.04 / 12);
Console.WriteLine(p);