What is the difference between units/hr and mL/hr?

Units per hour is the pharmacological dose — the actual amount of drug delivered per hour. mL per hour is the physical pump rate — how fast the bag empties. The relationship depends on concentration: mL/hr = (units/hr) ÷ (units/mL). Both values are needed: units/hr confirms the dose is correct, mL/hr is what you program into the pump.

How is concentration calculated from the bag?

Concentration (units/mL) = Total units in bag ÷ Total volume in mL. For example, a bag containing 25,000 units of heparin in 250 mL gives 100 units/mL. This number is then divided into the desired units/hr to get the pump rate in mL/hr.

Why is heparin dosed in units rather than mg?

Heparin potency varies by batch and is standardized by bioassay in International Units (IU), not by mass. Dosing in units/hr ensures consistent anticoagulant effect regardless of the heparin source or lot number. The same logic applies to insulin (units) and other biologics.

What weight should I use for weight-based dosing?

Most heparin protocols specify actual body weight (ABW). Some institutions cap the weight used at a defined maximum (e.g. 100 kg) to avoid supratherapeutic dosing in obese patients. Always follow your institutional protocol and confirm weight basis with the ordering provider.

Is this calculator a substitute for clinical judgment?

No. This tool is a mathematical reference only. All IV orders must be verified by a licensed nurse, pharmacist, or physician before administration. Always double-check against the original order, the physical label on the bag, and your institution's protocol.

IV Units Per Hour Calculator

Name: IV Units Per Hour Calculator
Availability: InStock
Author: Nham Vu

Enter your ordered dose (units/hr or units/kg/hr) and bag concentration to get the infusion pump rate in units per hour and mL per hour.

Infusion Parameters

Dose Type

Flat units/hr Weight-based

Ordered Dose

units/hr

Bag Concentration

Total Units in Bag

Total Volume (mL)

Enter infusion parameters and click Calculate Rate.

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Summary

Enter your ordered dose (units/hr or units/kg/hr) and bag concentration to get the infusion pump rate in units per hour and mL per hour.

How it works

Select the dose type: flat units/hr or weight-based units/kg/hr.
Enter the ordered dose (e.g. 1,000 units/hr or 18 units/kg/hr for heparin).
If weight-based, enter the patient's weight in kg.
Enter the bag concentration: total units and total volume in mL.
The calculator computes units per hour, concentration in units/mL, and the pump rate in mL/hr.
Review the result panel and use the copy button to transfer the rate to your documentation.

Use cases

Calculate heparin infusion rate from a weight-based protocol (e.g. 18 units/kg/hr).
Determine insulin drip rate from a flat units/hr order.
Verify a pharmacist-prepared bag concentration against the ordered rate.
Cross-check an existing pump setting before administering a unit-dosed IV.
Support nursing students learning IV drip rate calculations.
Quickly convert between units/hr and mL/hr at the bedside.
Recalculate the pump rate after a bag concentration change.
Validate protocol-driven titration steps against the physical bag.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu