We aim to be transparent about how every number on Plenvest is produced. Our calculators use standard, well-established finance formulas, state their assumptions plainly, and run entirely in your browser — we do not store the values you enter.
Data sources
- Contribution limits: verified 2026 IRS figures — 401(k) elective deferral $24,500, catch-up $8,000 (age 50+) / $11,250 (ages 60–63), $72,000 annual-additions cap; IRA limit $7,500 with a $1,100 catch-up. Where we project these forward, we index them by a cost-of-living rate you choose, using IRS-style rounding.
- Return assumptions: illustrative only. A long-run diversified portfolio has historically returned roughly 7% after inflation, but that is a historical average, not a forecast — you set the rate.
- Your inputs: balances, contributions, rates, and time horizons you provide.
How each tool is built
- Compound / Savings / Retirement / Roth: convert your nominal rate to an effective monthly rate (EAR), then compound month by month with your contribution.
- 401(k): models your contribution as a percent of salary, adds the employer match, and enforces the indexed IRS limits, capping the match against the annual-additions limit.
- Roth IRA: caps your annual contribution at the indexed IRS limit (plus age-50 catch-up).
- Mortgage: standard amortization, M = P·i / (1 − (1+i)⁻ᴺ), with optional extra payments to model early payoff.
- How much to retire: target nest egg = desired income ÷ safe withdrawal rate, inflated to your retirement year, compared with your projected trajectory.
- Traditional vs Roth: equal-contribution comparison that reinvests the Traditional tax deduction in a taxable side account (and taxes its gains), so both paths cost the same out of pocket.
Limitations
These tools are simplifications. They generally assume a constant return and constant rates, and they do not model market volatility or sequence-of-returns risk, taxes on withdrawal (except where a tool explicitly compares tax treatment), state taxes, RMDs, Social Security, the Roth income (MAGI) phase-out, or future changes to tax law. Results are estimates, not guarantees. They are educational and are not financial, tax, or investment advice — see our Terms.