The Five Funds, In Plain English
The TSP keeps it simple: five core funds. The G Fund holds special-issue government securities — it can never lose a dollar, and it never earns much. The F Fund tracks the bond market. The C Fund tracks the S&P 500 and has done the heavy lifting in most postal employees’ balances over the last decade. The S Fund covers small and mid-cap U.S. companies, and the I Fund covers international markets. L Funds are simply pre-mixed blends of these five that get more conservative as your target date approaches. The dashboard above shows historical returns for each — use the allocation modeler to see the weighted return of your actual mix. For a deeper walkthrough of each fund, see our TSP funds explained guide.
The Match: Free Money With a Catch
USPS automatically contributes 1% of your basic pay whether you contribute or not, then matches your contributions dollar-for-dollar on the first 3% and fifty cents on the dollar for the next 2%. Contribute 5% and you capture the full 5% match — an instant 100% return before the market does anything. The catch: the match is paid per pay period. Max out the $23,500 annual limit in September and your contributions stop — and so does the match for the rest of the year. In 2026’s 27-pay-period year, that means dividing your target across 27 checks, not 26. The limit tracker above turns red before you hit the wall.
What Compounding Actually Does
Run the default projection: a $70,000 balance, $500 per pay period, the 5% match on a $65,000 salary, 22 years at a steady 7%. You’d contribute about $427,500 total (including the match) and finish with roughly $1.17 million — growth does more than half the work. At historical fund returns the number climbs far higher, but plan on conservative assumptions and let the upside surprise you. The 4% rule column translates any balance into sustainable monthly income, which is how your TSP plugs into the retirement picture alongside your FERS annuity and Social Security.
Common Mistakes
Contributing less than 5% is leaving guaranteed money on the table — fix that before anything else. Parking decades of savings in the G Fund feels safe but historically hasn’t outrun inflation by much; safety has a cost too. Non-career employees note: CCAs, PSEs, and MHAs can contribute but don’t receive matching until conversion to career. And if you’re deciding between Roth and traditional contributions, remember your FERS annuity and Social Security already fill your lower tax brackets in retirement — our taxes guide explains how the pieces interact. Past performance doesn’t guarantee future results; verify current returns at tsp.gov.