Resources · Full vs Partial Optional
Can I work part-time after reaching Optional?
Short answerYes. Once you reach Full Optional, the portfolio already covers your spending and any income is bonus. What people usually mean by this question is different: 'If I expect part-time income later, can I stop the full-time job sooner?' That's Partial Optional, an earlier milestone. Every $100/mo of expected income shaves $30,000 off the Partial target, as long as the income keeps flowing.
Two dates matter here. Full Optional is portfolio-only and doesn't move with future-income assumptions. Partial Optional lands earlier but only holds while the income lasts. Below: a calculator that shows both, a worked example, and the formulas.
Calculator
See both dates against your numbers
Type in your numbers. Slide the part-time monthly income and how long you expect it to continue. The calculator shows Full Optional (portfolio-only) and Partial Optional (portfolio plus ongoing income), and flags whether the Partial date actually lands inside your income window or after it.
36%
Funded (Full Optional)
Years to Partial Optional
OCT 2034
Full Optional: APR 2038
Pull-forward: 42 months
Part-time income (post-tax, monthly)
Income continues for
Full Optional target
$1.80M
Partial Optional target
$1.35M
Target reduction
-$450K
Partial Optional lands 42 months before Full Optional — assuming the $1500/mo continues indefinitely. If it stops, you fall back to the Full Optional target.
Two dates Full Optional is the portfolio-only target and never moves with future-income assumptions. Partial Optional assumes the $1500/mo is post-tax, net of work expenses, and continues indefinitely. If the income stops before Full Optional, the target snaps back to the full number.
Assumes a 7% average real return (after inflation) and a 4% withdrawal rate.
Full Optional and Partial Optional are two different milestones
Full Optional is set by one number. How much invested does a 4% withdrawal need to cover your yearly spending forever? At $60,000 of spending, that's $1.5M. At $40,000, it's $1M. This number doesn't change if you plan to earn more later. It's the portfolio-only answer, and it's the one that keeps working when the part-time gig ends.
Partial Optional is a smaller, earlier target that assumes some spending gets covered by ongoing income. If you'll bring in $18,000 a year part-time, the portfolio only has to cover $42,000, so the target collapses to $1.05M. About $450,000 less to save, but only while the $18,000 a year keeps coming in.
Every $100/mo of ongoing income moves the Partial Optional target down by $30,000. Trinity Study math, run in reverse. It doesn't move Full Optional. If you're already at or past Full Optional, taking on part-time work doesn't bring the milestone any closer. You already have it. It just changes what the money you earn is for.
Worked example · illustrative
Full Optional vs Partial Optional side by side
Case study — Chen, 52 — illustrative case study, thinking about light consulting
Chen has $650,000 in her 401(k) and brokerage. She saves $1,800 a month and spends about $72,000 a year. She's planning on 8 to 10 years of light consulting after leaving her senior role, roughly $1,500/mo post-tax. She wants to know how much sooner she can leave, and what happens when the consulting winds down.
Balance
$650,000
Monthly save
$1,800
Annual spend
$72,000
Consulting
$1,500/mo · 10 yrs
Full Optional target: $1,800,000 (25 × $72,000). Chen is 36% funded today. Full Optional lands about 15 years from now, at age 67. It doesn't move.
Partial Optional target: $1,350,000 (25 × $54,000, after $18,000 of consulting covers the rest). About $450,000 less to save. Portfolio hits that target about 11 years from now, at age 63. Roughly 4 years sooner than Full Optional.
Does the 10-year window cover it? Yes. Partial Optional lands at year 11 and consulting runs for 10 years after that (through year 21). She reaches Full Optional in year 15, safely inside the window. The consulting bridges Partial to Full and then stops without breaking the plan.
If consulting ends early: if Chen only consults for 3 years, Partial Optional at year 11 arrives after her income has already stopped, so it isn't a real milestone. Her actual date is Full Optional, at age 67. The calculator above flags this. Try dropping "Income continues for" to 3 years and watch the summary change.
Inside the app
This decision, inside Project Optional
The same math runs in the Scenarios Lab through two levers. Drop-to-part-time (contribution changes before Optional) and Work-for-fun (post-Optional income, which is where Partial Optional lives). Layer either one against your other scenarios to see the combined effect.
The math
Assumptions and formulas
Same engine as the rest of the app.
Full Optional Number = Annual Spending ÷ 4%
Partial Optional Number = (Annual Spending − Ongoing Part-Time Income) ÷ 4%
Or in plain words:
Every $100/mo of part-time income ⇒ $30,000 less needed in the portfolio to hit Partial Optional.
- 7% real return. Both targets stay flat in today's dollars.
- 4% safe withdrawal rate. Fixed on this page; adjustable in the app.
- Part-time income is post-tax and net of work expenses. If the number is gross, discount for taxes before entering it.
- Partial Optional only holds while the income lasts. If it stops before you reach Full Optional, the target snaps back to the full number.
- Income grows with inflation over the duration you set. Nominal-only or fading income (a consulting practice that trails off) erodes Partial Optional faster than this page shows.
- No income variability or vacancy modeled. Consulting, rental, and small-business income are lumpier in real life than any calculator captures. Treat Partial Optional as a best case; Full Optional is the honest floor.
- No Social Security. Factor it in as additional ongoing income after your claim age.
FAQ
What people ask about this
What kinds of income actually count? Anything you can reasonably project as recurring monthly income for the duration you set. Consulting, teaching, a book royalty stream, a rental you'd keep managing, seasonal work. The more durable and inflation-linked, the closer Partial Optional is to a real milestone. Lumpy or variable income makes it a best case, and Full Optional stays the honest plan.
Aren't I asking about after Optional? Sometimes, in which case the answer is that you already reached Optional and part-time is a lifestyle choice. Most people typing this question are actually asking whether they can leave the full-time job sooner because they expect to earn something afterwards. That's Partial Optional.
Does this change how much I have to save now? Not directly. You still contribute what you contribute. What changes is which milestone you're aiming at. Partial arrives sooner but only holds while the income holds. Full is the one that doesn't need anything else to keep working.
What if I'm not sure the income will last? Model both. One scenario where it does, one where it doesn't. Save both in the Scenarios Lab and compare. For most people the honest answer is somewhere between the two dates.
Keep reading
Should I quit my high-paying job? →
The pre-Optional version. Switching to lower-paid full-time work instead of dropping the hours later.
Can I afford a sabbatical? →
The one-year version. Same math trick applied to a single break instead of ongoing income.
Should I sell my rental and stop working? →
The asset-conversion version. Same milestone question, income from cash flow instead of a job.
Membership
Save this plan and see it next to your real numbers
Enter your numbers, turn on the Work-for-fun scenario in the Scenarios Lab, and stack it against every other decision at once.