What's the difference between simple and compound interest?

Simple interest pays a fixed amount each period based only on the original principal. Compound interest reinvests earnings, so future interest is calculated on a growing balance. Over time, compounding produces significantly more growth.

What is APY and how is it different from APR?

APY (Annual Percentage Yield) accounts for compounding — it's the actual annual return you earn. APR (Annual Percentage Rate) is the stated rate before compounding effects. A 5% APR compounded daily has an APY of about 5.13%.

Does compounding frequency really matter?

Yes, but the difference between daily and monthly compounding is small. The biggest gains come from moving to a higher rate. Daily compounding on 5% yields about 5.13% APY vs 5.12% for monthly — a modest difference.

How long does it take money to double?

Use the Rule of 72: divide 72 by your annual interest rate. At 6%, money doubles in roughly 12 years. At 1%, it takes 72 years. This calculator shows you the exact time-to-double for any rate.

📈Investing

How Much Interest Will You Earn on Your Savings?

How much interest will you earn on savings?

What This Does

Every dollar sitting in savings is either working for you or falling behind inflation. The difference between a 0.5% savings account and a 5% high-yield account on $50,000 is over $2,200 per year — compounding makes that gap even wider over time. This calculator shows you exactly how much interest you'll earn based on your principal, rate, compounding frequency, and time horizon. Whether you're comparing savings accounts, evaluating a CD offer, or figuring out when your money will double, this tool gives you the full picture. Simple interest pays the same dollar amount each period — it's straightforward but less powerful. Compound interest reinvests your earnings, so each period's interest is calculated on a growing balance. The more frequently interest compounds (daily vs. annually), the more you earn — and this calculator lets you compare both side by side. Use the results to make smarter decisions: Is that "high-yield" savings account actually high yield? Would moving your emergency fund to a 5% account make a material difference? How long until your savings reach a target balance? Run the numbers once and you'll know exactly where you stand.

When Should You Use This?

→Comparing two savings accounts or CDs with different rates and compounding frequencies
→Calculating how much interest a fixed deposit will earn over a set term
→Figuring out when your savings will reach a specific dollar target
→Evaluating whether moving money to a high-yield account is worth the hassle
→Understanding the difference between APR and APY on a savings product

Example Scenario

Maria has $25,000 in a traditional savings account earning 0.5% APY. Her bank is now offering a 13-month CD at 5.1% compounded daily. She uses this calculator to compare: at 0.5% annually, she earns just $125 in a year. At 5.1% compounded daily, the same $25,000 earns $1,308 — more than 10x as much. The CD locks her money up, but for an emergency fund she rarely touches anyway, the $1,183 difference is compelling. She opens the CD.

Interest Calculator

Compound vs Simple · APY · Frequency · Rate Sensitivity · Schedule

Results update in real time as you adjust any input.

Principal (Starting Amount)

Annual Interest Rate (APR)

HYSAs: ~4.5–5% · CDs: ~4–5% · Money market: ~4%

Compounding Frequency

Most HYSAs and savings accounts compound daily

Time Period (Years)

years

About This Calculator

This interest calculator computes compound and simple interest for any principal, rate, compounding frequency, and time period. APY is calculated precisely from APR using the formula (1 + APR/n)^n − 1. All five standard compounding frequencies are supported: daily (365×/year), monthly (12×), quarterly (4×), semi-annual (2×), and annual (1×). Results update in real time as you adjust any input. The compounding bonus — the extra earned by reinvesting interest — is calculated separately to show the true value of compound vs simple interest.

The Growth tab renders a stacked area chart of principal (indigo) and compound interest (accent) growing to maturity, with a dashed line for simple interest total. A composition breakdown shows the percentage split between principal, simple interest, and the compounding bonus. The Compare tab shows a bar chart of interest earned at each compounding frequency and a line chart of interest vs rate (1–10%), with your current rate marked as a larger dot. The Schedule tab shows a bar chart of each year's individual interest earned — illustrating the compounding acceleration effect visually — plus a full year-by-year table with simple balance, compound balance, cumulative interest, and that year's interest.

An interest score (0–100) reflects the annual return quality: higher rates, longer periods, and larger principals score higher. Dynamic accent colours: emerald (Excellent, ≥85), indigo (Strong, ≥70), amber (Moderate, ≥50), orange (Low Yield, ≥30), red (Poor Yield). A below-inflation warning appears when the rate falls below 2.5%. The doubling time is calculated using the exact formula ln(2) / [n × ln(1 + r/n)] rather than the Rule of 72 approximation, for precision.

Results are estimates only and do not constitute financial, tax, or legal advice. Consult a qualified professional before making financial decisions.