Tutorial: Savings Growth Calculator
In this tutorial, you are a financial services company setting up a savings growth calculator in RuleX. By the end, you will have the same Excel model powering two different consumer experiences: a JSON API your bank partners can integrate into their own products, and a web form your customers can use directly in the browser.
What you will build
A calculator that projects the final value and total interest earned on a savings deposit at a fixed annual rate. It takes three inputs:
| Input | Description |
|---|---|
principal |
The initial deposit amount |
annual_rate |
The annual interest rate as a decimal (e.g. 0.05 for 5%) |
years |
The investment period in years |
And returns two outputs:
| Output | Description |
|---|---|
final_amount |
The value of the deposit at the end of the term |
interest_earned |
The total interest earned over the term |
Steps
- Upload a Data Source: upload the Excel model to RuleX
- Define a Schema: declare which cells are inputs and which are outputs
- Create an Endpoint: give the model a URL your bank partners can call
- Call via the JSON API: see how bank partners integrate the API
- Add Data Validations: reject invalid inputs before they reach the model
- Add Fixed Inputs: create a partner-specific endpoint with a promotional rate locked in
- Publish a Web Form: give customers a browser interface, no code required
- Write Tests: validate the model against known inputs before deploying
- Return a Scenario Comparison: return dynamic arrays using range and spill range output types
Before you start
You will need a RuleX account. Sign up at demo.rulex.coverstack.in for free if you do not have one.
Throughout this tutorial, API examples use https://<your-domain> as the base URL.
Replace it with the address of your RuleX api domain URL:
| Setup | Base URL |
|---|---|
| Full hosted access | https://<your-domain> |
| Self-hosted exported server | http://localhost:8000 |