Savings Growth Calculator

How to use Greenlight's compound interest calculator

Saving can feel abstract, especially for kids. But our compound interest calculator helps show how small (but steady) deposits can grow over time. Whether you're saving for a future car, college, or just teaching smart money habits, this tool helps visualize the power of savings and compound interest.

You can use our savings growth calculator to:

• Estimate savings based on age

• Compare different Greenlight plan savings rates (up to 6%*)

• View how different deposits and regular contributions impact savings

• See how earned interest adds up over time

It’s a hands-on way to introduce the concept of compound interest, and to see the impact of good saving habits, year after year.

What is compound interest?

Compound interest is interest you earn on your savings, and on the interest your savings have already earned. In other words, your money makes more money over time.

Here’s a quick example: Let’s say your child deposits $100 and earns 5% interest yearly. After the first year, they’ll have $105. In year two, they’ll earn interest on that $105, not just the original $100, so the growth starts to speed up.

The frequency of compounding matters too. If interest is compounded annually, it’s calculated once a year. But if it’s compounded daily, the interest is calculated and added every day, so the balance grows a little faster. The more often interest is added, the bigger the impact over time.

Learn to earn, save, and invest together.

With a debit card of their own, kids and teens learn to spend wisely, keep an eye on balances, and track their spending. Big money dreams? Set savings goals and start investing with as little as $1 — with your approval on every trade.

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How do I calculate interest?

You don’t need to be a math whiz to understand how savings grow, especially with a tool that does the number crunching for you.

The calculator uses a few simple inputs: 

• How much you’re starting with

• How much you’ll contribute regularly

• How often you plan to save

• Your child’s savings age range

• The interest rate

Here’s an example: Let’s say your 12-year-old is saving for their first car. They start with $150, contribute $50 a month, and earn 5% interest annually. By the time they turn 18, they could have $4,375.

But what if you just added the money manually without earning any interest? That same savings would only total $3,750. The extra $625 is the magic of compound interest doing its thing.

Where can I earn compound interest?

Not every account earns compound interest, but the right ones can help your savings grow faster. If you’re setting money aside for your child’s future or helping them build their own savings habits, it’s worth knowing which accounts actually put your money to work. Here are a few of the most common places where compound interest comes into play.

• High-yield savings accounts (HYSAs). These pay more interest than standard bank accounts.

• Certificates of deposit (CDs). You earn interest in exchange for locking away your money for a set time.

• Money market accounts. A mix between checking and savings, often with better rates.

• Greenlight savings reward. With Greenlight Max, Infinity, and Family Shield plans, kids can earn from 1% to 6% annually on their savings.*

Even a small difference in rates can lead to a big difference in long-term growth, especially for kids who start young.

6 ways to maximize compound interest

So, how can you make the most of compound interest? These six simple habits can help your family grow savings.

1. Start early. The earlier your child starts saving, the more time their money has the potential to grow. Even a small head start can make a difference.

2. Contribute consistently. Regular deposits, even $5 or $10 a week, can add up and earn even more interest.

3. Look for high rates. Not all accounts offer the same rates. Greenlight’s higher-tier plans, for example, offer savings rewards up to 6%*, which can give your child’s savings a serious boost.

4. Minimize fees. Watch out for hidden fees that can chip away at your interest. Choosing low- or no-fee accounts helps your money grow uninterrupted.

5. Reinvest your earnings. If your account earns interest, keep it in the account, so it will continue to earn more over time.

6. Be patient. Compound interest is powerful, but not always quick. The longer you let it work, the more impact it can have. Hang in there; it’s worth it.

Built for them. And for you.

Both you and your kids download the Greenlight app — with tailored experiences. They check off chores, you automate allowance. They spend wisely, you set flexible controls. They build healthy financial habits, and you cheer them on.

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