Monthly compounding plus the number present bias hides: how much future value you lose by starting a year later.
Educational estimates only. Not personalized advice. Data targets 2026 US rules.
Behavioral lens: Present bias
Present bias makes “I will start next year” feel free. On a 20-year clock it is not free, it is a five-figure hole in future value that never shows up on a to-do list.
Waiting one year to start costs about $25,870 in future value at these assumptions.
Automate the contribution you just modeled
PsyFi turns a one-time compound-interest tab into a monthly transfer you do not have to renegotiate with present-you.
Start your free trialOr get the app
Enter starting amount, monthly contribution, expected annual return, and years.
Read future value next to total contributions and interest earned.
Use “cost of waiting 1 year” as the number that decides whether you start this month.
Compound interest is simple arithmetic. Starting is not. Present bias, overweighting today relative to a later self, is why people understand 7% for 20 years and still leave cash in a checking account “until things calm down.”
Worked example using this page’s defaults: $10,000 today plus $500 each month at 7% for 20 years becomes about $299,160. You put in $130,000. Markets (under that assumption) add about $169,160. Delay the same plan by one year and you give up about $25,870 of that future value, more than two years of the $500 contribution, gone because the start date slipped.
That wait penalty is the second number. The first number people recite is the comfortable monthly amount. The second number is what “I’ll start in January” actually costs. If $25,870 feels abstract, divide it by 12: you are paying roughly $2,150 a year for the privilege of not opening the account yet.
Use a commitment device, not more motivation. Schedule the first transfer for payday. Name the account after the goal, not “brokerage.” Re-run this calculator when the contribution or the timeline changes. Insight without an automatic debit decays by Friday.
These figures are educational. Returns, fees, and taxes vary. Confirm compounding examples with Investor.gov and a qualified professional before you invest. PsyFi exists to turn the wait-cost moment into a habit, not to pick securities.
Authoritative sources
Months of runway at 3, 6, and 12 month targets with anxiety-buffer framing.
Behavioral lens: Normalcy bias
Assets minus liabilities with percentile-style framing for progress, not comparison.
Behavioral lens: Social comparison
Monthly savings needed for a goal date with commitment-device framing.
Behavioral lens: Implementation intentions
See purchasing power change over time and counter money illusion.
Behavioral lens: Money illusion
It is future value if you start now minus future value if the same plan starts 12 months later. The default example, $10,000 plus $500 a month at 7% for 20 years, grows to about $299,160. Waiting a year costs about $25,870.
No. 7% is a common long-run educational assumption, not a forecast. Re-run at 4% and 10% to see how sensitive the wait penalty is. This is not investment advice.
No. Results are nominal and pre-tax. Inflation shrinks purchasing power; taxes on interest, dividends, or withdrawals change what you keep. Confirm details with Investor.gov and a tax professional.
Yes. Every PsyFi free tool runs in your browser with no signup. We pair clear math with behavioral science so you can decide without creating an account.
No. Inputs stay on your device. Nothing you enter is sent to PsyFi servers.
No. These are educational estimates for 2026. Confirm current rules with the IRS, SSA, CFPB, or a qualified professional before acting.
Estimates for education only. Not financial, tax, mortgage, or legal advice. US federal and state rules change. Verify current figures with the IRS, SSA, or a qualified professional before acting. PsyFi tools add behavioral context; they do not replace personalized planning.
