Introduction
The PSA Density Calculator shows how much PSA you have for the size of your prostate. PSA is a protein made by the prostate. A blood test measures it. But a big prostate can make more PSA on its own, even with no cancer. That is why doctors also look at PSA density (PSAD).
The math is simple. You divide your total PSA by your prostate volume:
PSA density = total PSA (ng/mL) ÷ prostate volume (cc)
This tool works in two ways. If you have an MRI or ultrasound report with three measurements (length, width, and height), use Dimensional Mode. The calculator finds your prostate volume with the ellipsoid formula (L × W × H × 0.5236), the same math used by our Prostate Volume Calculator. If your report already lists a volume, use Direct Volume Mode and type it in.
You get your PSA density right away, plus a risk tier. A PSAD under 0.10 is low. Between 0.10 and 0.15 is borderline. Above 0.15 may point to a higher chance of prostate cancer, and your doctor may talk to you about a biopsy.
The calculator also gives you a step-by-step solution, a risk scale, a chart, and ready-to-copy report text in five languages. It accepts cm, mm, or inches for size, and ng/mL, µg/L, ng/dL, or ng/L for PSA. If you need to convert measurements by hand first, the mm to inches calculator and cm to inches calculator can help.
This tool is for learning and quick checks. It does not replace advice from your doctor. Always go over your results with a urologist.
How to use our PSA Density Calculator
Enter your prostate size and your total PSA blood level. The calculator gives you your prostate volume, your PSA density in ng/mL/cc, and what that number means for prostate cancer risk.
Pick your mode: Choose Dimensional Mode if your MRI or TRUS report lists three prostate measurements. Choose Direct Volume Mode if your report already gives a prostate volume.
Length (AP): Type the front-to-back size of the prostate from the sagittal view. Pick cm, mm, or inches from the drop-down next to it.
Width (LR): Type the widest left-to-right size from the axial view, then pick the unit.
Height (SI): Type the top-to-bottom size, from the base to the apex, then pick the unit.
Prostate Volume: In Direct Volume Mode, type the volume from your MRI, ultrasound, or pathology report. Pick cc (mL), L, in³, or mm³. Our volume conversion calculator handles other unit swaps if your report uses something unusual.
Total PSA: Type your total serum PSA from a blood test taken near the same time as the scan. Pick ng/mL, µg/L, ng/dL, or ng/L.
Display volume in: Choose the unit you want the prostate volume shown in. PSA density is always shown per cubic centimetre, with an in³ value beside it.
Report language: In the copy box, choose English, Spanish, French, Italian, or Dutch for the written report text.
Buttons: Press Calculate to see your results, Load Example to try sample numbers, or Reset to clear the form.
What Is PSA Density?
PSA density (PSAD) compares the amount of PSA in your blood to the size of your prostate. PSA stands for prostate-specific antigen. It is a protein made by the prostate gland. A blood test shows how much of it you have, in ng/mL.
The problem with PSA alone is that a big prostate makes more PSA, even when nothing is wrong. Many older men have an enlarged prostate (called BPH, or benign prostatic hyperplasia). Their PSA can look high just because the gland is large. PSA density helps sort this out by dividing the PSA level by the prostate volume.
The Formula
PSA density = total PSA (ng/mL) ÷ prostate volume (cc)
The answer is written in ng/mL/cc. One cc is the same as one mL. It is a ratio, much like the cholesterol ratio or the BUN/creatinine ratio used in other lab work — a single number that adds context to a raw result.
How Prostate Volume Is Measured
Doctors get prostate volume from an MRI scan or a transrectal ultrasound (TRUS). Sometimes the report gives the volume right away. Other times it lists three measurements: length (front to back), width (left to right), and height (top to bottom). Volume is then found with the ellipsoid formula, because the prostate is shaped a bit like an egg:
Volume = length × width × height × 0.52
All three measurements must be in centimeters. A normal young adult prostate is about 20–25 cc. It often grows larger with age. The same ellipsoid idea shows up in general geometry tools such as the Sphere Volume Calculator and the broader Volume Calculator.
What the Numbers Mean
- Under 0.10 ng/mL/cc — Lower chance of prostate cancer. A high PSA is more likely from gland size.
- 0.10 to 0.15 ng/mL/cc — Borderline. Doctors look at other facts, like age, family history, exam findings, and MRI results.
- Above 0.15 ng/mL/cc — Higher chance of prostate cancer. Doctors often use this as a reason to talk about a biopsy.
Why Doctors Use It
PSA density can cut down on biopsies that are not needed. A man with a PSA of 6 ng/mL and a 60 cc prostate has a PSAD of 0.10. That is reassuring. A man with the same PSA of 6 ng/mL but a 25 cc prostate has a PSAD of 0.24. That result is more worrying, even though both blood tests read the same. PSAD is also used in active surveillance, where low-risk cancer is watched over time instead of treated right away. Other urology tools work alongside it, such as the PVR Calculator for post-void residual urine, the Urine Output Calculator, and the GFR Calculator or Creatinine Clearance Calculator for kidney function before treatment.
Things to Keep in Mind
PSA density is one clue, not an answer. Other things can push PSA up for a short time, such as a urine infection, prostatitis, a recent catheter, riding a bike, or ejaculation. Some medicines, like finasteride and dutasteride, lower PSA by about half. Volume numbers can also differ between MRI and ultrasound, and between two people reading the same scan. Always go over your results with a urologist, who will look at your PSA trend, exam, MRI score, and health history together. For other imaging and risk scores you may see in a report, try the TIRADS Calculator, the Adrenal Washout Calculator, or the Breast Cancer Risk Calculator. General health measures like BMI, waist-to-hip ratio, and the BSA Calculator may also come up in your visit.