PSA Velocity Calculator

Calculate the rate of change in PSA over time, along with PSA doubling time — measures of how quickly a value is moving rather than where it currently sits.

👨‍⚕️ Lab Value📐 Velocity = ΔPSA / Δtime; doubling time = ln(2) × Δt / ln(PSA₂/PSA₁)🏥 Health

Earlier PSA (ng/mL)

Later PSA (ng/mL)

Months between the two tests

Third PSA (ng/mL, optional)

Months from first to third test (if using)

Please enter valid values.

Formula & Reference

Variable	Symbol	Formula	Units
PSA Velocity Calculator	—	Velocity = ΔPSA / Δtime; doubling time = ln(2) × Δt / ln(PSA₂/PSA₁)	ng/mL per year

Step-by-Step Examples

Example 1

Slow Rise

PSA 3.2 to 3.6 ng/mL over 24 months.

Change = 0.4 ng/mL
Time = 2.0 years
Velocity = 0.4 / 2.0 = 0.20 ng/mL/year
Below the 0.75 threshold

✓ 0.20 ng/mL/year — slow rise

Example 2

Rapid Rise

PSA 3.2 to 4.6 ng/mL over 12 months.

Change = 1.4 ng/mL
Time = 1.0 year
Velocity = 1.4 ng/mL/year
Doubling time = ln(2) × 1 / ln(4.6/3.2) = 1.91 years

✓ 1.40 ng/mL/year — above threshold

Example 3

Two Points Misleading

PSA 4.0 then 5.1 over 6 months, but the second test followed a recent cycling trip.

Apparent velocity = 1.1 / 0.5 = 2.20 ng/mL/year
But cycling can transiently elevate PSA
A repeat test under standard conditions is needed before interpreting

✓ Velocity unreliable — confounded measurement

Real-World Applications

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Trend Over Snapshot

A rising trend can carry information that a single value within the normal range does not.

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Doubling Time

In men already diagnosed, PSA doubling time is used in assessing biochemical recurrence and disease kinetics.

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Active Surveillance

Velocity and doubling time are monitored in surveillance protocols as one signal of whether disease behaviour is changing.

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Consultation Context

Bringing a series of dated PSA values to an appointment is more useful than a single recent number.

Common Mistakes to Avoid

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Calculating velocity from only two values

PSA fluctuates biologically between tests. Guidelines generally recommend at least three values over 18 to 24 months before drawing conclusions from a trend.

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Ignoring what can spike a single reading

Recent ejaculation, vigorous cycling, urinary tract infection, prostatitis, digital rectal examination, or catheterisation can all raise PSA transiently.

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Treating 0.75 ng/mL/year as diagnostic

The threshold comes from screening research and has been questioned in subsequent studies. It is a prompt for discussion, not a diagnosis.

Frequently Asked Questions

What is PSA velocity? ▾

The rate at which PSA changes over time, expressed in nanograms per millilitre per year.

What PSA velocity is concerning? ▾

Above 0.75 ng/mL per year is the most commonly cited threshold, though its value as an independent predictor has been debated in the literature.

How many PSA tests do I need for a reliable velocity? ▾

At least three values spanning 18 to 24 months. Two points are heavily influenced by normal biological variation between tests.

What is PSA doubling time? ▾

The time it would take PSA to double at the current rate of change. Short doubling times, particularly under three years, attract more clinical attention.

What can cause a temporary PSA rise? ▾

Recent ejaculation, vigorous cycling, urinary infection, prostatitis, a recent prostate examination, or any urological instrumentation.