Why This Calculator Is Different
Most retirement calculators give you one number: "You need $1.2 million." That's nice, but what does it mean for your monthly life? Can you afford your mortgage? Will you need to downsize?
Sagery shows you your projected monthly income after taxes — the money that actually hits your bank account. It also runs Monte Carlo simulations so you see not just the average case, but the range of possible outcomes including worst-case scenarios.
Step 1: Getting Your Inputs Right
The calculator asks for a few key numbers. Here's how to get the most accurate inputs. Current age and target retirement age are straightforward. For current savings, add up all retirement accounts (401k, IRA, Roth IRA) plus any investments you're earmarking for retirement.
Monthly savings is where people get tripped up. Include your 401k contributions, employer match, IRA contributions, and any additional investment account deposits. Don't include emergency fund savings — that's a separate bucket.
Pro tip: use the actual numbers from your most recent pay stub and account statements. Approximations compound over 30 years. A $200/month error in savings translates to roughly $200,000 difference in projected outcomes.
Step 2: Understanding the Results
The calculator shows three key numbers. Portfolio at retirement is your projected total nest egg. Monthly withdrawal is how much you can safely take out each month. Monthly net income is what you'll actually receive after taxes — this is the number that matters most.
The success rate percentage tells you: out of 1,000 simulated market scenarios, how many resulted in your money lasting through retirement? A 90%+ success rate is generally considered good. Below 75% suggests you may need to adjust your plan.
Don't panic if the numbers aren't what you hoped. The whole point is to see where you stand NOW so you can make adjustments while you still have time.
Step 3: Running What-If Scenarios
This is where the real value lives. Once you see your baseline numbers, start asking "what if" questions. What if I save an extra $200/month? What if I retire at 67 instead of 65? What if I get a windfall of $50,000?
The Pro version lets you save unlimited scenarios side-by-side. But even with the free calculator, you can adjust inputs and see how each change impacts your projected income. Focus on the levers you actually control: savings rate, retirement age, and expense reduction.
The most impactful lever for most people is time. Retiring two years later doesn't just mean two more years of saving — it also means two fewer years of withdrawals and two more years of compound growth. That triple effect can shift your monthly income by 15-20%.
Common Mistakes to Avoid
Don't use your gross salary when the calculator asks for income — use net take-home pay if that's what the field requests. Don't forget to include Social Security (the calculator estimates this for you). Don't assume a single "average" return tells the whole story — that's why we run Monte Carlo.
The biggest mistake: running the calculator once and never coming back. Your financial situation changes. Run it annually, or after any major life event (marriage, kids, job change, inheritance). Think of it as a financial check-up, not a one-time diagnosis.
Finally, remember that no calculator predicts the future. These are projections based on historical patterns and your assumptions. Use them as a planning tool, not a guarantee.
📌 Key Takeaways
- 1Use actual numbers from pay stubs and account statements — not rough estimates
- 2Monthly net income (after taxes) is the number that matters most for retirement planning
- 3A success rate above 90% across Monte Carlo scenarios is generally solid
- 4The biggest improvement lever for most people is retirement timing, not returns
- 5Run the calculator annually or after major life changes
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