What is Coast FIRE for couples?
Coast FIRE for a couple means the two of you have invested enough that, without adding more, your shared savings can grow into what you'll both need once you've stopped working. It's one plan, not two: one pot, one budget, two ages and two Social Security checks, and often two different retirement dates.
How the calculator works
Most retirement calculators assume one person. Couples end up running the numbers twice and adding them together, which goes wrong as soon as one of you stops working before the other. This calculator plans for the household as a whole.
- Savings and spending are shared. Enter what you have invested between you, what you put away each year and what you'll spend together in retirement.
- Each of you has your own age, your own Social Security or pension, and your own health insurance cost until 65.
- Ages in the plan are yours, the first person's. Your partner's benefits still start at their own age.
- The plan runs until the younger of you turns 95, so a partner a few years younger adds a few years of spending.
When one of you stops first
Add the years when only one of you works. Give the age you'll be when the first of you stops, and the take-home pay of whoever keeps working. In those years that paycheck covers part of your spending and your savings cover the rest. "Both retired at" is your age when the second of you stops.
The numbers you get
Your FIRE number is what you need invested in the year you're both retired. Your Coast FIRE number is that amount discounted back to today. The headline answer is the earliest age you can stop saving and still get there, counting the years one of you is still bringing in money. How we calculate has the details.
Coast FIRE number = FIRE number ÷ (1 + r) ^ (years until you're both retired)r is your yearly return after inflation and fees. The default is 5%.
Three worked examples
All three use a 5% return after inflation, a 4% withdrawal rate, no tax on withdrawals, and plans that run until the younger partner turns 95. Social Security amounts are after tax and in today's dollars.
Example 1: one of you stops four years earlier
You're 40 and your partner is 38. Between you there's $250,000 invested, and you add $30,000 a year. You plan to stop at 58, while your partner keeps working, and their employer's health plan, for four more years on $50,000 take-home. Once you've both stopped, you'll spend $72,000 a year and pay $9,000 each for health insurance until 65.
| Your age | 40 |
|---|---|
| Partner's age | 38 |
| Invested today | $250,000 |
| Saving per year | $30,000 |
| Only one of you working | 58 to 61 |
| Their take-home | $50,000 |
| Both retired at | 62 |
| Spending per year | $72,000 |
| Health insurance, each | $9,000 a year until 65 |
| Your Social Security | $28,000 a year from 67 |
| Partner's Social Security | $20,000 a year from 67 |
| FIRE number at 62 | $934,444 |
|---|---|
| Coast FIRE number today | $319,440 |
| Progress toward it | 78.3% |
| Can stop saving at | 44 |
| Calendar year | 2030 |
| Invested at that point | $433,180 |
Four more years of saving gets them to $433,180 at 44. From there the money grows untouched until 58, pays the gap while one paycheck is still coming in, and reaches $934,444 by the time they're both retired. Note that the Coast FIRE number of $319,440 assumes no withdrawals before 62, so the plan has to clear a higher bar than that.
Example 2: the same couple, stopping together at 58
Now both of them leave work when you turn 58. There's no paycheck in the bridge years, and they pay for their own health insurance from the start.
| Both retired at | 58 |
|---|---|
| Spending per year | $72,000 |
| Your Social Security | $28,000 a year from 67 |
| Partner's Social Security | $20,000 a year from 67 |
| FIRE number at 58 | $1,151,907 |
|---|---|
| Coast FIRE number today | $478,641 |
| Can stop saving at | 50 |
| Calendar year | 2036 |
Stopping together raises the target to $1,151,907. From 58 their savings pay the whole budget plus two health insurance bills, with no paycheck coming in. They'd have to keep saving until 50 instead of 44, so in this plan four years of one income are worth six years of saving.
Example 3: a six-year age gap
You're 45 and your partner is 39. You have $400,000 invested, save $25,000 a year and want to stop together when you turn 60, which makes your partner 54. You'll spend $65,000 a year.
| Your age | 45 |
|---|---|
| Partner's age | 39 |
| Invested today | $400,000 |
| Saving per year | $25,000 |
| Both retired at | 60 |
| Spending per year | $65,000 |
| Health insurance, each | $9,000 a year until 65 |
| Your Social Security | $30,000 a year from 67 |
| Partner's Social Security | $18,000 a year from 67 |
| FIRE number at 60 | $946,043 |
|---|---|
| Coast FIRE number today | $455,063 |
| Progress toward it | 87.9% |
| Can stop saving at | 48 |
| Calendar year | 2029 |
The plan has to last until your partner turns 95, when you'd be 101, so the money covers 42 years from 60. Your partner also pays for health insurance for 11 years before Medicare, against 5 for you. Even so, they're at 87.9% of their Coast number, and three more years of saving gets them there.
Retiring at different times
Couples rarely stop working in the same year. One of you may be older, or burned out sooner, or the other may like their job. A staggered exit can make early retirement cheaper in three ways.
- The paycheck that keeps coming in covers part of your spending, so your savings are drawn down more slowly in the first years.
- In the US, the working partner's employer plan can often cover you both. Health insurance before Medicare at 65 is one of the biggest costs of retiring early.
- Your savings get a few more years to grow before they have to carry the whole budget.
Social Security works the same way. Each of you can claim at a different age, and a later claim pays more for life. If one of you earned much less, they may be able to claim a spousal benefit based on the other's record. Your my Social Security accounts show what each of you can expect.
Why couples get different answers from different tools
- One person or two. A single-person calculator can't count two Social Security checks starting at different times, or a partner who keeps working.
- Whose age ends the plan. Planning to the older partner's 95th birthday leaves the younger one short. We plan to the younger partner's.
- Health insurance. Two people paying for coverage before 65 can cost more than many tools assume, especially when one partner is much younger.
- Adding two plans together. Running separate numbers for each of you and summing them double-counts some costs and misses the years when one income supports both.
What this calculator doesn't do
- It doesn't model the death of one partner. In real life, spending usually drops and one Social Security check stops or is replaced by a survivor benefit.
- It doesn't keep separate accounts or work out when each of you can reach a 401(k) or IRA without penalty.
- It uses one flat tax rate on withdrawals for the household, not your actual brackets or filing status.
- Spending is one household number for retirement, plus an optional one for the years when only one of you works. It doesn't change after that.
Common questions
Can we plan Coast FIRE together if we keep separate finances?
Yes, as long as you'll share costs in retirement. Enter what you both have invested and what you'll spend together. If you plan to keep your money fully separate, run your own numbers on the Coast FIRE calculator.
How do we enter two Social Security benefits?
Add one income for each of you and pick whose it is. Each one starts at that person's own age, so a benefit your partner claims at 67 starts when they turn 67, whatever age you are then.
What if one of us retires ten years before the other?
That works too. Set the years when only one of you works to cover the whole stretch. A long single-income period can do more for the plan than extra years of saving, as long as that one paycheck covers most of your spending.
Whose age should go first?
Either. The plan uses the first person's age for the timeline and still ends when the younger of you turns 95. Most couples put the person who'll stop working first.
Do we have to be married?
No. The math is the same for any two people sharing a budget. Marriage does matter for things this calculator doesn't cover, like spousal and survivor benefits and filing jointly.
What if one of us plans to work part-time?
Part-time pay goes in the same place as a full-time paycheck: the take-home pay for the years only one of you works. If you both plan to go part-time, the Barista FIRE calculator is built around that.
Sources
- US Social Security Administration. Retirement benefits. www.ssa.gov/benefits/retirement
- US Social Security Administration. my Social Security (your personal benefit estimate). www.ssa.gov/myaccount
- Cooley, Philip L., Carl M. Hubbard and Daniel T. Walz. "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable." AAII Journal, February 1998. Usually called the Trinity study.
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