How do you calculate a CLABSI rate?

Divide the number of CLABSIs in a location by the number of central line days in that location for the same period, and multiply by 1,000. NHSN reports it as CLABSIs per 1,000 central line days.

How do you calculate a CAUTI rate?

The same way, with indwelling urinary catheter days as the denominator: CAUTIs ÷ urinary catheter days × 1,000.

What is the device utilization ratio?

Device days divided by patient days for the same location and period — for example central line days ÷ patient days. It shows how much of the unit’s patient time involves the device, and is a target for reducing device use.

Should I compare my rate with another hospital’s?

Be careful: raw rates do not adjust for differences in patient populations. NHSN uses the standardized infection ratio (SIR) for risk-adjusted comparisons with the national baseline.

Free tool · CIC® exam topic

CLABSI & CAUTI rate calculator

Infections per 1,000 device days and the device utilization ratio, calculated the way NHSN defines them.

Result

Infections per 1,000 device days: 1.62
Device utilization ratio: 0.30

3 infections ÷ 1,850 device days × 1,000.

NHSN formulas

CLABSI rate = number of CLABSIs ÷ number of central line days × 1,000
CAUTI rate = number of CAUTIs ÷ number of urinary catheter days × 1,000
Device utilization ratio (DUR) = device days ÷ patient days

Device days are counted once a day for each patient with the device, for the same location and time period as the infections. NHSN also tracks a risk-adjusted standardized utilization ratio (SUR) for device use.

Worked example

An ICU reports 3 CLABSIs and 1,850 central line days in a quarter: 3 ÷ 1,850 × 1,000 = 1.62 CLABSIs per 1,000 central line days. With 6,200 patient days, the central line utilization ratio is 1,850 ÷ 6,200 = 0.30 — central lines were in place for about 30% of patient days.

Rates vs the SIR

Rates are useful for tracking one unit over time. To compare with the national baseline, NHSN uses the standardized infection ratio, which adjusts for risk factors — try the SIR calculator.

Test yourself: a CIC-style question

Which formula does NHSN use to calculate the CLABSI rate?

(Number of CLABSIs ÷ number of patient days) × 1,000
(Number of CLABSIs ÷ number of central line days) × 1,000
(Number of central line days ÷ number of CLABSIs) × 1,000
(Number of patient days ÷ number of CLABSIs) × 1,000

Show answer

B. (Number of CLABSIs ÷ number of central line days) × 1,000

NHSN calculates the CLABSI rate as the number of CLABSIs divided by central line days, multiplied by 1,000 — infections per 1,000 central line days.

Questions like this come up in the Surveillance and Epidemiologic Investigation domain of the CIC® exam. The 654 questions in the app each come with a written explanation.

FAQ

How do you calculate a CLABSI rate?: Divide the number of CLABSIs in a location by the number of central line days in that location for the same period, and multiply by 1,000. NHSN reports it as CLABSIs per 1,000 central line days.
How do you calculate a CAUTI rate?: The same way, with indwelling urinary catheter days as the denominator: CAUTIs ÷ urinary catheter days × 1,000.
What is the device utilization ratio?: Device days divided by patient days for the same location and period — for example central line days ÷ patient days. It shows how much of the unit’s patient time involves the device, and is a target for reducing device use.
Should I compare my rate with another hospital’s?: Be careful: raw rates do not adjust for differences in patient populations. NHSN uses the standardized infection ratio (SIR) for risk-adjusted comparisons with the national baseline.

Sources

Checked against these sources on October 21, 2026. For education and CIC® exam preparation only — not a substitute for your facility’s policies, NHSN’s official reports, or clinical judgment. Calculations run in your browser; nothing you enter is sent anywhere.