There are dozens of websites with free online 401k calculators, but the vast majority just "rent" usage of them from the vendors below. Paying them rent allows webmasters to put the retirement calculators on their site in a manner that makes it look like their site built them (when they really just go to a site like Dinkytown to calculate / display results). So most online 401(k) calculators are the same.

Please keep in mind that Tools for Money didn't make the money calculators listed below, they're just links to other free online financial calculator websites.

Most calculate the numbers as advertised, but there are so few input fields, that you can't account for most of the details that will dramatically alter Real World results.

This is page 1 of 11 of the free financial calculators:

401(k) Calculators

Basic Financial Calculators

Family Money Calculators

Real Estate Calculators

Debt Calculators

Investment Calculators

Retirement Calculators

Tax Calculators

College Calculators

Insurance Calculators

Business Owner Calculators

Time Value of Money and Financial Calculator Terminology

TVM = Time value of money, the basic concepts of what these financial calculators are all about. PV = Present Value (beginning investment values, or how much something is worth today). PMT = Payments (constant contributions or withdrawals each compounding period, usually added to or subtracted from the scenario monthly). I = Compound interest rate (interest rate or growth rate that is applied at each N compounding period). N = Number of compounding periods (how many times the calculations are done that compound money at the given interest rate, usually in months or years. E.g., If you have $100 and you compound, or add, 10% annual interest, then you'd have $110 as a future value over this one compounding period. If N=2, then it would compound twice, and your ending value would be $121, which is $110 plus 10%). FV = Future value (usually the result, or the amount of money accumulated over N compounding periods). P = Principal, or how much money is being lent or borrowed. ARM = Adjustable Rate Mortgage. APR = Annual Percentage Rate.

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Here's the List of Most Everyone's Free 401k Calculators:

Tip: The "number of inputs" tells how "good it is."

The fewer the number of input cells, the less amount of functions it performs. The fewer functions it performs, the less accurate it is, because it fails to account for important things, you can't control anything, and so the "lamer" it is. In general the lamer the free online calculator, the lamer the programming code is too, so there's many serious "errors" in their math.

So the more inputs the better.

The average number of inputs for all of the free rinky-Dinkytown 401(k) calculators below is around ten.

We did not run any numbers to test accuracy or anything, so caveat emptor and you get what you pay for, all applies here!

Listed in alphabetical order by their URL:

401k.fidelity.com - Links to their retirement calculators

401kcalculator.org - Nine inputs estimates FV in 30 years, then it has a chart that shows contributions and value over 30 years.

401khelpcenter.com - Has links to some of the most popular 401 calcs in the several to dozen input range

ADP's Calculate Your Savings by Integrating 401(K)& Payroll calculator

ADP's 401(k) calculator

ADP's 403(b) calculator

Alta Street - 401(k) savings calculator

Bloomberg.com - Ten-input 401(k) savings calculator