How do I see my compound interest broken down year by year?
Use a calculator that shows an actual table. One row per year. Starting balance, annual contributions, annual interest, ending balance. That is the only format where you can point at a specific year and see exactly when your interest earnings overtake your contributions. Most compound interest calculators online hide this table, show a truncated version, or replace it with a chart that looks impressive and tells you nothing.
Accruo shows the full table by default. Thirty years means thirty rows. Fifty years means fifty rows. The header sticks to the top while you scroll. You can copy the whole thing into a spreadsheet in two clicks.
That is the whole point of this article. If you came here looking for the year-by-year math, you already have your answer. The rest is context for why this feature is so rare, and what the numbers actually tell you when you look at them closely.
Why so few calculators show the year-by-year table
I audited the top eight compound interest calculators before building Accruo. Three of them showed a real year-by-year breakdown. Five either skipped it, buried it behind a tab, or replaced it with a static chart image from 2013.
There is a reason for this. A year-by-year table is a commitment. It has to be accurate for every row. Rounding errors that are invisible in a single final number become obvious when row 7's ending balance does not equal row 8's starting balance. Some calculators hide the table because they cannot afford to be audited row by row.
The more cynical reason is that the table gives you a reason to leave. Once you understand the shape of compounding, you do not need the calculator as much. Sites that sell advisor matches, high-yield savings accounts, or "learn the secrets of investing" courses are less interested in you leaving satisfied.
What the year-by-year table actually shows you
Take the scenario the Accruo homepage starts with. Initial deposit of $10,000, $500 added every month, 7 percent annual rate compounded monthly, 30 years.
In year 1, your $500 monthly contribution adds $6,000 to the pile. The account earns roughly $900 in interest. Your contributions are dominant. You are doing most of the work.
Somewhere around year 14, the line crosses. The account earns more interest in that single year than you contribute in that single year. Your money has started pulling its own weight.
By year 30, the account earns about $39,000 in that final year alone. Your $6,000 in yearly contributions is rounding error by comparison. The final ending balance lands just under $610,000, of which about $180,000 came out of your paycheck and the remaining $430,000 came from interest.
You cannot see that crossover point in a summary panel. You cannot see it in a stacked area chart, because charts flatten the eye. You can only see it in a table, at the row where the annual interest column exceeds the annual contributions column. That row is the one worth highlighting on a sticky note.
What is the compound interest formula, in plain language
The full formula with regular contributions is ugly on the page. The readable version goes like this.
Every compounding period, the account earns interest on whatever is already in it. That interest gets added back in. The next period, you earn interest on the original balance plus all the prior interest. And you have been adding contributions along the way, each of which also starts earning interest from the moment it arrives.
Two variables drive the curve. One is the annual rate. The other is how often the interest compounds. Daily compounding earns slightly more than monthly, which earns slightly more than annually, but the gap is smaller than most people think. Doubling the rate matters far more than doubling the compounding frequency.
Accruo lets you change both. The summary panel updates in real time. The table redraws every row. There is no Calculate button, because a calculator that makes you click a button to see a new answer is no longer really a calculator. It is a form.
How much will $500 a month grow over 30 years at 7 percent
About $610,000 with a $10,000 starting deposit and monthly compounding. About $570,000 if you start at zero. The exact figure depends on whether you contribute at the start or end of each month, and on compounding frequency. Accruo defaults to end-of-month contributions compounding monthly, which matches the SEC Investor.gov reference calculator within a dollar.
If this number surprises you in either direction, that is normal. Compounding curves are counterintuitive. Your intuition extrapolates linearly. Compounding does not. The only way to calibrate your sense of what is possible is to look at the table and see where the numbers actually land in each year.
This is also why the Roth IRA and 401(k) advice you have been reading makes sense. The accounts are tax-advantaged wrappers around the same compounding math. A $500 monthly contribution to a Roth IRA at 7 percent produces the same gross growth as a $500 monthly contribution to a taxable brokerage account. The difference is at the end, when Roth distributions are tax-free and brokerage capital gains are not.
What the numbers do not include
Accruo shows pre-tax, pre-fee, pre-inflation estimates. Those three things will reduce the real value of the final number by meaningful amounts over a 30-year horizon.
Taxes depend on the account type. A 401(k) or traditional IRA defers the tax bill to retirement. A Roth IRA settles it now. A taxable brokerage account owes capital gains on growth. A high-yield savings account owes ordinary income tax on interest every year you earn it.
Fees compound too. An expense ratio of 0.50 percent a year sounds small. Over 30 years, it reduces your final balance by roughly 14 percent. Over 40 years, by roughly 18 percent. That is a real number hiding inside the chart.
Inflation is the quiet one. A 7 percent nominal return with 3 percent inflation is really a 4 percent real return. The $610,000 at year 30 buys what about $250,000 buys today. That is still a lot of money. It is just a different number than the headline.
Accruo does not model any of these. A future version might. For now, the tool assumes you want to see the clean compounding curve without the correcting factors, because the uncorrected number is the one that motivates people to start saving in the first place. The corrections can come once you are already in motion.
Using the table to make an actual decision
Three ways I use a year-by-year breakdown when I am working through a real scenario.
First, find the crossover year. The year where annual interest exceeds annual contributions is your "compounding has taken over" milestone. Everything before that is you pushing. Everything after is the account pushing.
Second, find the doubling years. Write down your balance at year 10. Look for the year it doubles. Then look for the year it doubles again. At 7 percent, this happens roughly every 10 years. At 5 percent, roughly every 14. This is the rule of 72 made tangible.
Third, delete rows. Take the 30-year table, delete the last 10 years, and see what you get. That is what happens if you stop contributing or cash out early. The difference between the 20-year and 30-year final balance is bigger than the entire 20-year balance itself, which is the real argument against touching retirement accounts early.
You can do all three of these on Accruo without typing anything twice. The table recalculates when you drag a slider. The crossover year shifts visibly. The doubling point moves. The last ten years of exponential growth either appear or disappear depending on where the slider lands.
That is what a compound interest calculator is supposed to do. Not sell you something. Not collect your email. Show you the math, row by row, with no page reload.
Open Accruo and drag the years slider from 10 to 30. Watch what the table does in the last third of the horizon. That is the number worth seeing.