Calculators for making money compound
Five focused tools built on one idea: money left to grow multiplies on itself. Project a lump sum, a monthly habit, or both — and see what decades of compounding actually do.
The essentials
Compound Interest
the classicThe flagship tool: lump sum plus contributions, with compounding frequency, inflation and tax options — watch decades of growth on one chart.
Open calculatorFuture Value
FVWhat will your money be worth later? A lump sum, regular deposits, or both — with the ordinary/due timing toggle and a year-by-year table.
Open calculatorPresent Value
PVFuture money is worth less than money in hand. Discount any future amount back to today's dollars at your chosen rate.
Open calculatorWays to invest
Lump Sum Investment
one-timeA bonus, an inheritance, idle savings: see what a single investment grows into, how fast it doubles, and what it's worth after inflation.
Open calculatorMonthly Investment
habitNo lump sum needed — just consistency. Project a fixed monthly investment, with optional annual raises as your income grows.
Open calculatorHow compounding builds wealth
The order that turns a rate of return into a plan — start with the engine, then choose how you'll feed it.
See the engine
Start with the flagship tool. Feed it a starting amount, a return and a horizon, and watch how the curve bends upward as growth earns growth.
Invest a lump sum
Got a bonus or an inheritance sitting idle? See what a single amount becomes over time, how quickly it doubles, and what inflation leaves of it.
Build the habit
No windfall needed. A fixed monthly amount, invested consistently and raised as your income grows, is how most wealth is actually built.
Value money across time
Compare amounts at different dates on equal terms — grow a sum forward to its future value, or discount a future sum back to today.
What makes money grow
Compound interest is often called the eighth wonder of the world for a reason: your returns start earning returns of their own, and the effect accelerates the longer it runs. Over a few years the difference from simple interest is small. Over a few decades it is the whole game.
Three levers control the outcome — how much you start with, how much you add, and how long you leave it alone. Time is the most powerful of the three, which is why starting early beats starting big.
Compound interest
Interest earned on both your principal and the interest already added. Each period's growth is calculated on a slightly larger base, so the balance curves upward rather than rising in a straight line.
Contributions
Regular deposits added on top of the starting amount. Small, consistent contributions often outgrow a larger one-time sum, because each one gets its own runway to compound.
Compounding frequency
How often interest is added — yearly, monthly, daily. More frequent compounding lifts the effective return slightly, though the gap narrows as frequency rises.
Time horizon
The number of years the money grows. Because compounding accelerates, the final years contribute far more than the first — so an early start is worth more than a bigger balance later.
Rate of return
The annual growth rate. Modest differences compound into enormous gaps over decades, which is why fees and a percent or two of return matter so much.
Inflation
The quiet drag on real growth. A balance that looks large in future dollars buys less than the number suggests — always sanity-check the result in today's money.
What $10,000 becomes at 7%
A single $10,000 investment, no further contributions, growing at 7% a year. Notice how much of the total arrives in the final decade.
| Years | Balance | Growth | Multiple |
|---|---|---|---|
| 10 | $19,672 | $9,672 | 2.0× |
| 20 | $38,697 | $28,697 | 3.9× |
| 30 | $76,123 | $66,123 | 7.6× |
| 40 | $149,745 | $139,745 | 15.0× |
Illustrative only, at a constant 7% with annual compounding — real returns vary year to year. The pattern is the point: the money roughly doubles every decade, so the last ten years add more than the first thirty combined.