Most people set their 401(k) contribution once during onboarding and never revisit it. That default 3% feels safe, but it leaves serious money on the table — especially if your employer matches up to 6%. The difference between contributing 3% and 6% on a $75,000 salary over 30 years can exceed $400,000 in total retirement savings, and that gap only widens with annual raises factored in.
You don't need to pay someone $200/hour to model this. Here's how to project your 401(k) growth yourself and actually understand what the numbers mean.
Step 1: Know Your Inputs
Before you run any projection, gather four numbers:
- Your gross salary — not take-home, gross. For 2025, the median U.S. household income sits around $80,000 according to the Bureau of Labor Statistics.
- Your contribution percentage — what you currently put in, and what you're considering bumping it to.
- Your employer match — the formula matters. "100% match on the first 4%" is different from "50% match on the first 6%." Check your plan summary.
- Your expected annual raise — 3% is a reasonable baseline for most industries.
You also want to know the IRS 401(k) contribution limits. For 2025, the employee elective deferral limit is $23,500, with an additional $7,500 catch-up if you're 50 or older.
Step 2: Run a Year-by-Year Projection
This is where most people stall. Spreadsheets work but take time to set up correctly — you need to account for contribution limits that increase over time, employer match caps, and compounding returns that vary by year.
The 401(k) calculator on EvvyTools handles this in one pass. Enter your salary, contribution rate, employer match formula, expected raise, and estimated return rate. It builds year-by-year projections that show your balance at each age, broken down by your contributions, employer contributions, and investment growth.
The value isn't just the final number — it's seeing how each variable moves the needle. Bumping your contribution from 6% to 10% on a $75,000 salary adds roughly $3,000/year in contributions, but with a 7% average return over 25 years, that extra $3,000/year compounds into an additional $200,000+.
Step 3: Compare Scenarios Side by Side
Run the projection at least twice: once at your current contribution rate, once at the rate you're considering. Pay attention to how quickly employer matching maxes out. If your employer matches 50% of the first 6%, there's no matching benefit to contributing 8% versus 6% — though the tax-deferred growth still matters.
If you're weighing a W-2 position against contract work, the employer match gap is one of the biggest hidden costs. A contractor earning the same gross pay gets zero match, which can mean $5,000-$10,000 less per year flowing into retirement. The article 1099 vs W-2: How to Compare Your Real Take-Home Pay breaks down exactly how to quantify that difference.
One More Thing
Don't forget about vesting schedules. Your employer's contributions might not be fully yours until you've been at the company for 3-5 years. A 4% match means nothing if you leave after 18 months and only 25% has vested. Factor that into your projection — the calculator gives you the gross picture, but your actual take depends on how long you plan to stay.
Run the numbers once a year, especially after raises. A 5-minute check on EvvyTools can confirm whether your contribution rate still makes sense — or reveal that you've been leaving free money on the table.
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