Psa Velocity Calculator

Enter the initial and subsequent PSA levels and the time duration into the calculator to determine the PSA velocity.

Medical note: This calculator is for educational purposes only and is not medical advice. PSA velocity is not diagnostic of prostate cancer and should not be used alone to make health decisions; PSA can change due to non-cancer causes and measurement/clinical context matters—discuss your PSA trend with a licensed clinician.

PSA Velocity Formula

PSA velocity is the average rate of change in prostate-specific antigen (PSA) between two test results. In plain terms, it tells you how quickly the later PSA value is rising or falling relative to the earlier value over a measured time interval.

PSAV = \frac{PSA_2 - PSA_1}{t}

Variable	Description	Common Unit
PSAV	PSA velocity, or the average change in PSA per unit of time	ng/mL/year, ng/mL/month, or ng/mL/day
PSA₁	Earlier PSA measurement	ng/mL
PSA₂	Later PSA measurement	ng/mL
t	Elapsed time between the two tests	years, months, or days

If your time interval is not already in years, the same idea still applies. The calculator simply divides the PSA change by the elapsed time in the unit you choose.

PSAV_{year} = \frac{PSA_2 - PSA_1}{Years}

PSAV_{month} = \frac{PSA_2 - PSA_1}{Months}

PSAV_{day} = \frac{PSA_2 - PSA_1}{Days}

How to Calculate PSA Velocity

Enter the earlier PSA result as PSA1.
Enter the later PSA result as PSA2.
Enter the exact time between the two tests in years, months, or days.
Subtract the earlier PSA from the later PSA.
Divide that difference by the elapsed time.

This means the calculator is finding the slope between two points: the change in PSA over the change in time.

Interpreting the Result

Positive PSA velocity: the later PSA is higher than the earlier PSA.
Zero PSA velocity: there is no net change between the two results.
Negative PSA velocity: the later PSA is lower than the earlier PSA.

PSAV > 0 \Rightarrow PSA_2 > PSA_1

PSAV = 0 \Rightarrow PSA_2 = PSA_1

PSAV < 0 \Rightarrow PSA_2 < PSA_1

Example Calculation

Assume an earlier PSA result of 4.2 ng/mL, a later PSA result of 5.1 ng/mL, and an elapsed time of 18 months.

\Delta PSA = 5.1 - 4.2 = 0.9

t = \frac{18}{12} = 1.5 \text{ years}

PSAV = \frac{0.9}{1.5} = 0.6 \text{ ng/mL/year}

If you prefer the monthly rate for the same data:

PSAV = \frac{0.9}{18} = 0.05 \text{ ng/mL/month}

Why the Time Interval Matters

The same PSA change can produce very different velocity values depending on how much time passed between tests. A shorter interval creates a larger rate, while a longer interval creates a smaller rate.

Scenario	Result
PSA increases by 1.0 ng/mL over 1 year	$PSAV = \frac{1.0}{1} = 1.0 \text{ ng/mL/year}$
PSA increases by 1.0 ng/mL over 2 years	$PSAV = \frac{1.0}{2} = 0.5 \text{ ng/mL/year}$

Practical Tips for Using the Calculator

Use the earlier lab result for PSA1 and the later lab result for PSA2.
Make sure both PSA values are in the same unit, typically ng/mL.
Use the actual time elapsed between the tests instead of rounding too aggressively.
If your tests are several months apart, entering months directly can reduce conversion mistakes.
A two-point velocity is an average change over one interval, not a complete long-term trend.

What This Calculator Tells You

The net PSA change between two dates
The average rate of that change
Whether the change is upward, flat, or downward
The rate in yearly, monthly, or daily terms depending on the selected time unit

Important Context

This calculator is useful for quantifying change, but it does not identify the reason for that change. It is best viewed as a math tool for trend estimation between two measurements. Because PSA interpretation depends on clinical context, testing conditions, and the broader pattern over time, this result should be discussed with a licensed clinician rather than used alone to make medical decisions.