How this calculator works
A sabbatical is a planned break from paid work, usually a few months to a year. The fund has to cover the costs that continue while you are not earning, plus anything extra the break involves. This calculator multiplies your monthly spending during the break by the number of months, then compares that target with what you have already saved. In time mode it finds how many months of depositing at your current rate are needed. In saving mode it works back from a fixed start date to the monthly deposit required. Two costs are easy to miss. First, a break also interrupts retirement contributions and may reduce a pension entitlement, which is not in the target. Second, a buffer for the unexpected is wise: a break is exactly when a surprise expense is hardest to absorb. Many planners suggest adding 10% to 20% to the basic figure. The return assumption should be conservative, since money needed within a few years should not be invested in volatile assets.
Formula
Fund needed = monthly spending during the break x months off. Months to save = ln((F + D/i)/(P + D/i)) / ln(1+i), where P is the amount already saved, D the monthly deposit, i the monthly return and F the fund needed. Monthly saving required = (F - P(1+i)^n) x i / ((1+i)^n - 1) for n months. At a zero return, the time is (F - P)/D and the deposit is (F - P)/n.
Worked example
Six months off at $2,500 a month needs $15,000. With $5,000 already saved and $800 a month at 3%, the remaining $10,000 takes about 12.14 months, so 13 months of saving. If the break is three years away, the required monthly saving is about $253.31. With no return at all, the same $10,000 gap at $800 a month takes 12.5 months.
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Frequently asked questions
How much buffer should I add?
Add 10% to 20% for the unexpected. A sabbatical has no employer to fall back on, and an unplanned cost during the break can force an early return to work or debt.
Should I include health insurance?
Yes, if you lose employer coverage during the break. That cost can be large and is easy to overlook. Add the monthly premium to your break spending.
What about retirement contributions?
They stop during the break, which reduces your eventual retirement balance. The calculator does not model that loss; adding the missed contributions to the fund target is one way to account for it.
Where should the sabbatical fund be held?
In safe, accessible savings. The money is needed on a known date, so a fall in the market just before the break would be costly. Use a high-interest savings account or short-term deposit.