Future Value | Growth & Purchasing Power

Future Value Calculator

This calculator projects future value from a lump sum and fixed monthly contributions using compound interest (monthly, quarterly, annual, or continuous). It shows nominal balance, real purchasing power after inflation, and after-tax value using a single capital-gains rate on total gains at the horizon. Real return rate and strategy badge compare growth to inflation. Illustrative only, not tax or investment advice.

Updated June 9, 2026

How to use this calculator

Enter present value ($10,000 default), monthly contribution ($500), and years (20) in 01. Set return (7%), inflation (2.5%), and capital gains rate (15%) in 02; pick compounding frequency and payment timing in 03. The results card shows nominal FV (≈ $0.3M at defaults), real after-tax purchasing power, inflation gap, tax bite, compound velocity, and strategy badge. Sections 04–05 chart nominal vs real growth and list contributions, gains, and after-tax wealth. Illustrative only, not tax or investment advice.

Future value calculator: FV, real purchasing power, and tax

This calculator projects lump-sum plus annuity future value with monthly compounding by default, converts nominal balance to real purchasing power using your inflation rate, and applies a single capital-gains tax to total gains. Illustrative only, not tax or investment advice.

What this calculator does

Projects future value from an initial deposit and fixed monthly contributions at a constant annual return. You pick compounding frequency and whether contributions land at the beginning or end of each period. Inflation converts nominal FV to today's purchasing power; a single capital-gains rate reduces gains at the end of the plan. Outputs include inflation gap, compound velocity, real return rate, strategy badge, and a nominal vs real chart. It does not model changing rates, fees, withdrawal rules, or account-specific tax treatment.

Lump sum + contributions (discrete compounding):

$FV = PV\left(1+\frac{r}{n}\right)^{nt} + PMT \left[\frac{\left(1+\frac{r}{n}\right)^{nt}-1}{\frac{r}{n}}\right]$
PMT scales to the compounding period (monthly, quarterly, or annual). Beginning-of-period payments multiply PMT by (1 + r/n).
Real future value:

$\text{Real FV} = \frac{\text{Nominal FV}}{(1+i)^{t}}$
i = inflation rate, t = years. After-tax real FV uses nominal FV minus tax on gains, then divides by (1 + i)^t.
Real return rate:

$\text{Real return} = \left(\frac{1+r}{1+i} - 1\right) \times 100$

How the math works

Start with the default plan: $10,000 today, $500 added each month, and 20 years to grow at 7% with monthly compounding. The calculator compounds your opening balance and every contribution as they land at the end of each month. That produces a nominal future value of about $300,851, which is the large number on the results card.

Next it separates what you put in from what the market added. Your total contributions are $130,000 ($10,000 plus $500 × 240 months). Subtract that from the nominal balance and the gains are about $170,851. The tax field (default 15%) applies only to those gains, not to your deposits. That tax bill is roughly $25,628, leaving about $275,223 after tax.

Inflation is the last step. The calculator divides that after-tax balance by 20 years of 2.5% price growth to estimate what it would feel like in today's dollars: about $167,961 in real purchasing power. It also compares your 7% return to 2.5% inflation to get a real return of about +4.4%, which triggers the Wealth Builder badge. Compound velocity (~56.8%) is simply gains divided by the ending balance, so you can see how much of the total came from growth rather than from your own deposits.

Limits of the model

Your return and inflation rates stay fixed for the whole plan. Taxes apply once to total gains, not every year. No advisory fees, sequence-of-returns risk, or account rules (401(k), Roth, taxable). The section 04 chart shows inflation-adjusted nominal balances without tax; only the results card applies tax before converting to real purchasing power.

Future Value Calculator FAQ

How does this calculator compute future value?

Section 01–03 feed a lump sum plus fixed monthly contributions into standard FV formulas with your compounding frequency and payment timing. At defaults ($10,000, $500/mo, 20 years, 7%, monthly, end of period), nominal FV ≈ $300,851 (headline shows $0.3M).

What is the difference between nominal and real future value here?

Nominal is the projected account balance in future dollars. Real purchasing power in the results card divides after-tax nominal by (1 + inflation)^years. Default → real after-tax ≈ $167,961. The inflation gap tile is nominal minus inflation-adjusted nominal before tax (≈ $117,250 at defaults).

How does this calculator tax investment gains?

It applies your Estimated tax rate (default 15%) once to total gains at the end of the plan (nominal FV minus contributions). Default tax on gains ≈ $25,628; after-tax nominal ≈ $275,223. It does not model annual tax drag, ordinary income, or account type (Roth vs taxable).

What do the strategy badge labels mean?

Wealth Builder when real return >2%; Erosion Warning when 0–2%; Purchasing Power Crisis when negative. Real return = ((1 + return) ÷ (1 + inflation) − 1) × 100. Default 7% return and 2.5% inflation → about +4.4% → Wealth Builder.

What does compounding frequency change in this widget?

More periods per year slightly raise nominal FV because interest accrues sooner. Default is Monthly (12×/year) with monthly contributions. Continuous uses e^rt on the lump sum and an equivalent monthly annuity formula on contributions.

Beginning vs end of period payments?

End of period (default) matches most auto-invest schedules. Beginning of period multiplies each contribution by (1 + periodic rate) so payments earn a full extra period. The gap widens with larger monthly additions and more years.

What is compound velocity in the results panel?

Gains ÷ nominal FV × 100: the share of the ending balance from growth vs what you deposited. At defaults about 56.8% of nominal FV is gains and about 43% is the $130,000 you funded ($10,000 start + $500/mo × 20 years).

What do sections 04 and 05 show?

Section 04 charts nominal FV (solid) and inflation-adjusted FV (dashed) by year; the dashed line does not subtract taxes. Section 05 lists total contributions, total gains, and after-tax nominal in full dollars.

Sources & citations

References used for the calculation method and definitions. Links open in a new tab when available.

[1]

SEC – Investor.gov: Compound Interest (Glossary)

SEC glossary entry on compound interest, the mechanism behind nominal future value growth.

[2]

IRS – Investment Income and Expenses (Publication 550)

IRS overview of investment income and capital gains tax treatment referenced for the simplified after-tax layer.

Future Value Calculator

Asset foundations

Growth & erosion

Technical settings

Nominal vs. real value over time

Wealth breakdown