IntRacer offers a simple, instant way to track interest earned over time—based on your initial setup, with no need to link bank accounts or share personal data. Watch your balance grow in real time with continuous updates throughout the day.

Description of the App

This minimalist calculator app lets users enter a one-time setup including their principal amount, interest rates, and start date. It then calculates interest growth per minute and displays the current balance, total interest gained, and today’s earnings on demand, making it ideal for visualizing how money grows over time. Withdrawing funds temporarily reduces the interest rate to the low interest rate for 30 days, after which the higher rate automatically resumes.

Unlike traditional financial systems where interest and balance updates typically occur monthly or quarterly, this app updates interest growth every minute. This real-time calculation provides immediate insight into how your money accumulates, allowing you to trace your account’s growth dynamically and precisely at any moment, offering greater transparency and control over your finances.

How to Use It

Using this application is straightforward. On first launch, you’ll be prompted to enter your initial account details, including the principal amount, high and low annual interest rates, account start date, and preferred currency. The app continuously calculates interest growth on a per-minute basis, displaying your current balance, total interest earned, and today’s gain in real time. To update your account, use the Deposit or Withdraw buttons to enter transaction amounts and dates. You can also adjust the AER% interest rate along with its effective date, the app will automatically apply them as specified and recalculate your interest and total balance from that date onward.

To view your interest growth visually, tap the chart icon. You can choose to display either the accumulated interest or the total balance. To reset all data and start fresh, tap the trash icon.

Note: Any withdrawal will temporarily reduce your interest rate to the lower rate for 30 days. After this period, the higher rate will be restored automatically.

This app operates entirely offline—no internet connection or login required—ensuring your data remains private and secure at all times.

How interest is calculated

This app calculates interest based on the Annual Equivalent Rate (AER%) entered by the user. To provide accurate updates at different time intervals (monthly, daily, hourly, or by the minute), the following method is used:

We define:

• α = AER% / 100 (i.e., the AER expressed as a decimal)

• T = Number of compounding intervals per year

• β = Periodic interest rate = (1 + α)^(1/T) - 1 = AGR% / 100 / T

Each period, the balance is updated as: Balance(i+1) = Balance(i) * β

Below is the exsample of compounding intervals, periods per year, and AGR estimates when AER% = 5.

This method ensures that:

• Your interest updates match the compound growth implied by the AER.

• The balance reflects real-time compounding, not just annual totals.

• Accuracy is preserved whether you're viewing changes monthly or minute-by-minute.

Security

This app is built with your privacy and safety in mind from the ground up. It does not connect to the internet at any point, which means nothing you enter is ever transmitted or shared. You will never be asked to provide personal details such as your name, bank account number, or login credentials. The app functions entirely as a standalone calculator.

All information you enter, including the principal amount, interest rates, start date, and any adjustments, is stored only on your device using Apple’s secure @AppStorage system. This storage method keeps your data safely contained within the app’s sandbox environment, and it cannot be accessed by other apps or systems on your phone.

If you ever wish to clear your data, you can do so with a simple reset option built into the app. This action permanently deletes all stored values, restoring the app to its original state without leaving any trace of your information behind.

Because the app never communicates with external servers and never collects personal data, you can use it confidently knowing that everything stays private and fully under your control. It adheres strictly to Apple’s privacy guidelines for apps that run entirely on the user’s device.