How the calculator works
- Your FI number is the portfolio you need at retirement. It is set by your spending and withdrawal strategy and grows with inflation up to your retirement date.
- The coast line is that number discounted back with your expected market gain: FI number ÷ (1 + monthly gain) to the power of the months until retirement. Its value today is your coast number.
- Your savings plan runs month by month until your portfolio meets the coast line. From that month you can stop saving: growth alone takes it to your FI number by retirement.
- From retirement, the chart shows how your portfolio develops while you withdraw.
This is a projection, not financial advice. It assumes a constant market gain and inflation, no taxes or fees, and no withdrawals before retirement. Once you stop saving there is no new money as a buffer, so check your plan regularly.
Coast FIRE vs FIRE, Barista FIRE and Lean FIRE
All of them aim at financial independence. They differ in when you stop saving, when you stop working and how much you plan to spend.
| Type | Stop saving | Stop working | Suits you if |
|---|---|---|---|
| Coast FIRE | When you reach your coast number | At a normal retirement age | You like your work but want to stop saving and work with less pressure |
| FIRE → | When you reach your FI number | At the same time | You want to stop working as early as possible |
| Barista FIRE | When part-time income plus withdrawals cover your costs | Full-time work early, part-time later | You want out of full-time work before you reach your full FI number |
| Lean FIRE | When you reach a smaller FI number | Early, on a tight budget | You are happy to live on low spending |
| Fat FIRE | When you reach a large FI number | Early, with a generous budget | You want a comfortable lifestyle and accept saving longer |
Example: coast numbers at 25, 35 and 45
The same plan for each age: $2,000 a month in retirement at 65 with preserve capital, an average market gain of 8%, inflation of 2%, $50,000 invested today and $500 saved per month.
| Age today | Coast number today | Stop saving at |
|---|---|---|
| 25 | $42,778 | Already coasting |
| 35 | $75,763 | age 40 |
| 45 | $134,182 | Not before 65 |
The earlier you start, the smaller the coast number: at 25 the market has 40 years to do the work for you.
Frequently asked questions
What is a Coast FIRE number?
It is the amount you need invested today so that growth alone, without any more saving, reaches your FI number by retirement. The formula is FI number ÷ (1 + return) to the power of the years until retirement. With a $600,000 FI number, a 6% real return and 30 years to go, that is about $104,000.
Is Coast FIRE realistic?
Yes, if you start early and stay invested. The risk is that markets return less than you assumed, and after the coast point there are no new savings to make up for it. Check your progress every year and save again if you fall below the coast line.
What is the difference between Coast FIRE and Barista FIRE?
With Coast FIRE you keep working until retirement and only stop saving; your portfolio stays untouched until then. With Barista FIRE you leave full-time work early and your portfolio already pays part of your costs, topped up by part-time income.
Can I stop working once I am coasting?
Not completely. Coasting means you no longer need to save, but your income still has to cover your living costs until retirement. Many people use it to work part-time, change careers or take a break.
What market gain should I assume?
Many planners use 6% to 8% a year for a stock-heavy portfolio before inflation. A lower number gives you a safer, larger coast number. Change it in the settings to see how sensitive your result is.
Is my data stored?
No. The calculator runs in your browser. Your inputs are only kept in the page address so you can bookmark or share your plan.
Is this financial advice?
No. It is a projection based on the assumptions you enter. Real returns vary from year to year and are not guaranteed.
