CRI Dose & Infusion Rate Calculator
Use this tool to estimate drug delivery for a constant rate infusion (CRI). Enter patient, dose, and solution concentration values to calculate mg/hr and pump rate in mL/hr.
What is a constant rate infusion?
A constant rate infusion (CRI) is a way to deliver medication continuously over time so blood levels stay more stable than with intermittent bolus dosing. CRIs are common in anesthesia, pain management, sedation, and critical care because they help clinicians maintain a predictable therapeutic effect.
Instead of giving a single dose and waiting for it to wear off, a CRI delivers a set amount each minute or hour. The challenge is converting a prescribed dose (like mcg/kg/min) into a practical pump setting (mL/hr). That is exactly what this calculator does.
How this infusion rate calculator works
Step 1: Convert dose to mg/hr
- If dose is in mcg/kg/min: mg/hr = weight (kg) × dose (mcg/kg/min) × 60 ÷ 1000
- If dose is in mg/kg/hr: mg/hr = weight (kg) × dose (mg/kg/hr)
Step 2: Convert mg/hr to mL/hr
- mL/hr = mg/hr ÷ solution concentration (mg/mL)
Step 3: Optional preparation estimate
If you enter infusion duration and stock concentration, the tool also estimates total drug required and how many milliliters of stock solution are needed to prepare the infusion plan.
Why concentration matters
The pump can only deliver volume. Your order is usually in weight-based drug units. Concentration is the bridge between these two worlds. If concentration is entered incorrectly, the mL/hr output can be dangerously wrong. Always confirm concentration from the final mixed bag or syringe, not just the vial label.
Example use case
Suppose a 20 kg patient needs a drug at 3 mcg/kg/min, and your final syringe concentration is 0.5 mg/mL:
- mg/hr = 20 × 3 × 60 ÷ 1000 = 3.6 mg/hr
- mL/hr = 3.6 ÷ 0.5 = 7.2 mL/hr
Your pump setting would be approximately 7.2 mL/hr.
Common CRI calculation mistakes
- Mixing up mcg and mg (1000-fold error risk)
- Using patient weight in pounds instead of kilograms
- Entering stock vial concentration when calculator expects final mixed concentration
- Forgetting to update rates after concentration changes
- Rounding too early during multi-step calculations
Safety checklist before starting infusion
- Verify patient identity and accurate current weight
- Confirm prescribed dose, unit, and therapeutic range
- Double-check final mixed concentration and labeling
- Program pump carefully and have independent check when possible
- Monitor clinical response and adverse effects continuously
Important note
This calculator is an educational support tool and not a substitute for institutional protocols, pharmacist review, or clinician judgment. Always follow your local dosing guidelines and medication safety standards.