Moneysim - Savings Simulator
Moneysim answers a simple planning question: if I keep putting the same amount aside every month, where will I be in a few years? Enter what you have saved today, your monthly deposit, the number of years and an annual interest rate, and it shows the projected balance, how much of it is your own money and how much is interest.
Add a target amount, such as a house deposit, an emergency fund or the cost of a trip, and Moneysim tells you what percentage of that goal the plan reaches. A line chart traces the balance month by month so you can see how slowly compounding starts and how it gathers pace.
It works with any currency symbol you type, needs no account and keeps your chosen symbol in this browser for next time.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use Moneysim
- Set your currency. Type a currency symbol such as $, €, £ or ¥ in the Currency Symbol field. It is shown in front of the amounts and remembered for your next visit.
- Enter your starting point. Fill in Current Savings with what you already have and Monthly Savings with what you plan to add each month. Thousands separators are added as you type.
- Set a goal. Enter the Target Amount you are aiming for. It is used to show how much of the goal the plan achieves.
- Choose period and rate. Enter the Period in whole years and the Annual Interest rate in percent, for example 2.5 for 2.5% a year.
- Calculate. Tap Calculate. The Results card shows the future value, the principal you paid in, the interest earned and your target achievement percentage.
- Read the chart. Below the results, a line chart plots the balance for every month of the period. Change any input and calculate again to compare plans.
Features
- Future value of a regular savings plan
- Split between principal deposited and interest earned
- Target achievement as a percentage
- Monthly compounding from an annual interest rate
- Month-by-month growth chart
- Any currency symbol, remembered in your browser
- Thousands separators in the amount fields
- Interface in many languages
Understanding compound savings
How the calculation works
Moneysim divides the annual rate by 12 and runs through the plan one month at a time. Each month the deposit is added first and then that month's interest is applied to the whole balance, so every deposit starts earning straight away. For example, 1,000 today plus 100 a month for 10 years at 3% a year grows to roughly 15,360, of which 13,000 is your own money and about 2,360 is interest.
Why time matters more than you expect
With compound interest, interest is earned on earlier interest as well as on deposits. In the early years the effect is small and the chart looks almost like a straight line of deposits. Over longer periods the curve bends upward. Starting a few years earlier, even with smaller deposits, often beats saving more later. A rough rule of thumb, the rule of 72, says money doubles in about 72 divided by the annual rate years: around 24 years at 3%, 12 years at 6%.
Rates, inflation and fees
The rate you enter is assumed to stay fixed for the whole period, which real accounts rarely do. Savings rates change, investments rise and fall, and fees or taxes on interest reduce what you keep. Inflation also matters: if prices rise 2% a year, a balance earning 2% keeps roughly the same buying power. To see results in today's money, try subtracting your expected inflation from the interest rate.
Setting a realistic goal
A clear target makes a plan easier to stick to. If the achievement percentage is below 100, you can see which lever helps most: a higher monthly deposit, a longer period or a higher rate. Changing one input at a time and recalculating shows the trade-offs. Many people first build an emergency fund covering a few months of essential costs before saving toward other goals.
Frequently asked questions
Where is my data stored?
Only in this browser. Moneysim remembers your currency symbol locally, with no account and no server. Clearing your browser's site data removes it. The amounts you enter are not kept between visits.
Is interest compounded monthly?
Yes. The annual rate is divided by 12 and applied every month after that month's deposit is added.
Can I enter decimal amounts?
The money fields accept whole numbers. The interest rate field accepts decimals such as 1.5.
Does it account for inflation or tax?
No. It uses a fixed nominal rate. You can approximate real growth by entering the interest rate minus your expected inflation.
Which currencies are supported?
Any. The symbol is only a label; the calculation is the same for every currency.
What is different from the phone app?
The calculator is the same. The iPhone and Android apps show ads that a subscription removes; the web version has no ads or purchases.
Limitations of the web version
- Inputs and results are not kept after the page is reloaded; only the currency symbol is remembered
- The interest rate is fixed for the whole period
- Monthly deposits are the same every month
- Inflation, fees and taxes are not included
Disclaimer
Moneysim provides simple estimates for planning purposes only and is not financial advice. Actual returns, fees, taxes and inflation will differ. Consider speaking with a qualified financial adviser before making financial decisions.
Phone app
Moneysim is also available as an app for phones and tablets: