How to build a mortgage calculator in Bubble

The simplest way to build a mortgage calculator in Bubble is to place three inputs (loan amount, annual interest rate, loan term in years), then use a text element that calculates the monthly payment using Bubble’s “Calculate formula” inside the expression. You apply the standard mortgage formula using Bubble’s math functions: power, division, minus, etc.

Core Formula You Will Use

The monthly payment formula works in Bubble because Bubble supports math inside dynamic expressions:

Monthly Payment = (P × r) ÷ (1 − (1 + r)⁻ⁿ) Where P = loan amount, r = monthly interest rate, n = total months

How to Build It in Bubble

• Create three inputs: LoanAmount (number), InterestRate (number, as percent), LoanYears (number).
• Add a text element. In “Insert dynamic data,” build the formula using Bubble’s math operators.
• Convert annual rate to monthly: InterestRate / 100 / 12.
• Convert years to months: LoanYears × 12.

Working Expression Example

You’ll put this inside a text element’s dynamic expression. This uses real Bubble syntax:

// P = Input LoanAmount's value
// r = Input InterestRate's value / 100 / 12
// n = Input LoanYears's value * 12

(Input LoanAmount's value * (Input InterestRate's value / 100 / 12)) 
/ 
(1 - Power(1 + (Input InterestRate's value / 100 / 12), -(Input LoanYears's value * 12)))

Extra Tips

• If any input is empty, Bubble may show “NaN”. Wrap your text with a condition: When any input is empty → show 0 or blank.
• You don’t need backend workflows for this. All runs instantly on-page.
• To show total interest, add: (MonthlyPayment × n) − P using another text element.