How do I convert mcg/kg/min to mL/hr?

mL/hr = dose (mcg/kg/min) × weight (kg) × 60 ÷ concentration (mcg/mL). Example: 5 mcg/kg/min × 70 kg × 60 = 21,000 mcg/hr; with 400 mg in 250 mL (1,600 mcg/mL) the rate is 21,000 ÷ 1,600 = 13.1 mL/hr.

How do I calculate a heparin drip in units/hr?

mL/hr = units per hour ÷ units per mL. For 18 units/kg/hr in an 80 kg patient: 18 × 80 = 1,440 units/hr. With 25,000 units in 250 mL (100 units/mL) the pump rate is 1,440 ÷ 100 = 14.4 mL/hr. Always use your institution's weight-based heparin protocol.

How do I find the concentration of an IV bag?

Divide the drug amount by the total volume: 400 mg in 250 mL = 1.6 mg/mL = 1,600 mcg/mL; 4 mg in 250 mL = 16 mcg/mL; 25,000 units in 250 mL = 100 units/mL. Enter the bag as amount and volume and the calculator does this step.

What is the formula for gravity drip rate (gtt/min)?

Drip Rate (gtt/min) = [Total Volume (mL) × Drop Factor (gtt/mL)] ÷ Duration (minutes). Equivalently gtt/min = mL/hr × drop factor ÷ 60, so with 60 gtt/mL microdrip tubing gtt/min equals mL/hr. Divide gtt/min by 4 to count drops per 15 seconds.

What drop factor should I select?

Use the drop factor printed on the exact IV administration set packaging. Common macrodrip factors include 10, 15 or 20 gtt/mL, while microdrip tubing uses 60 gtt/mL; never infer the factor from the tubing name alone.

How long will an IV bag last?

Time (hours) = volume remaining (mL) ÷ rate (mL/hr). 750 mL at 125 mL/hr runs for 6 hours; if started at 08:00 it finishes at 14:00. Use the Time mode to get the finish clock time.

Can I back-calculate the dose from a running rate?

Yes. Select Rate → Dose, enter the current pump rate (mL/hr), the bag strength, the weight for per-kg units, and choose the dose unit to report.

Does this tool replace clinical judgment?

No. This calculator is strictly an educational and verification aid. Clinicians must independently verify orders, concentrations and pump settings, and use the pump drug library where available, before administration.

IV Infusion Rate Calculator

Turn a dose order (mcg/kg/min, mg/hr, units/hr, units/kg/hr, mU/min) and the bag strength (e.g. 400 mg in 250 mL) into a pump rate in mL/hr, back-calculate the dose from a running rate, get gtt/min for 10/15/20/60 gtt/mL tubing, or find when a bag will finish.

Pump rate (mL/hr) = dose per hour ÷ concentration.

Calculation Parameters

Calculation Mode

Total Infusion Volume (mL)

Infusion Duration

Tubing Drop Factor

Use the value printed on the exact administration-set package.

Enter the infusion parameters and click Calculate.

Governing Formulas

Dose → Pump Rate mL/hr = dose × kg × 60 ÷ concentration Drop “× kg” if not weight-based and “× 60” if dosed per hour.

Concentration conc = drug amount ÷ bag volume (mL) 400 mg / 250 mL = 1.6 mg/mL = 1,600 mcg/mL

IV Pump Flow Rate mL/hr = Volume (mL) ÷ Hours

Gravity Drip Rate gtt/min = mL/hr × Drop Factor ÷ 60

mL/hr to gtt/min by Drop Factor

Pump rate	10 gtt/mL	15 gtt/mL	20 gtt/mL	60 gtt/mL
10 mL/hr	2	3	3	10
20 mL/hr	3	5	7	20
25 mL/hr	4	6	8	25
50 mL/hr	8	13	17	50
75 mL/hr	13	19	25	75
100 mL/hr	17	25	33	100
125 mL/hr	21	31	42	125
150 mL/hr	25	38	50	150
200 mL/hr	33	50	67	200
250 mL/hr	42	63	83	250

Drops per minute, rounded to whole drops. Macrodrip sets are commonly 10, 15 or 20 gtt/mL; microdrip sets are 60 gtt/mL (gtt/min = mL/hr). Always confirm the package label.

• Unit standard: 1 lb = 0.45359237 kg; 1 g = 1,000 mg; 1 mg = 1,000 mcg; 1 unit = 1,000 milliunits; 1 hr = 60 min.

• Gravity limitations: Actual flow can change with fluid properties, equipment and patient factors. Follow the prescription, product labeling and institutional policy; use the required approved delivery device.

• Primary references: NCBI Nursing Skills: IV infusion by gravity; Queensland Health medication calculation formulae; NHS infusion calculations.

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Quick answer

Pump rate (mL/hr) = dose per hour ÷ concentration. For weight-based doses multiply by weight in kg, and for per-minute doses multiply by 60; concentration is drug amount ÷ bag volume. Example: dopamine 5 mcg/kg/min for 70 kg with 400 mg in 250 mL (1,600 mcg/mL) → 5 × 70 × 60 ÷ 1,600 = 13.1 mL/hr.

Examples

Order	Bag	Pump rate
Dopamine 5 mcg/kg/min, 70 kg	400 mg / 250 mL	13.13 mL/hr
Norepinephrine 8 mcg/min	4 mg / 250 mL	30 mL/hr
Heparin 18 units/kg/hr, 80 kg	25,000 units / 250 mL	14.4 mL/hr
Oxytocin 2 milliunits/min	30 units / 500 mL	2 mL/hr
1,000 mL over 8 hr, 15 gtt/mL set	—	125 mL/hr = 31 gtt/min

Choose Dose → Rate, enter weight, dose and bag strength, and check the step-by-step math.

Summary

This clinical math calculator solves four common infusion problems: converting fluid volume and duration into pump rates (mL/hr) and gravity drip rates (gtt/min); determining pump rates for dose orders (mcg/kg/min, mg/hr, units/hr, units/kg/hr, milliunits/min) from the bag strength; back-calculating the delivered dose from an operating pump rate; and finding infusion time and finish time from volume and rate. Calculations are for educational and cross-check purposes only; verify all medication orders against institutional protocols before administration.

How it works

Select a mode: Volume & Drip, Dose → Rate, Rate → Dose, or Time (volume ÷ rate).
For dose modes, enter the bag as drug amount and volume (e.g. 400 mg in 250 mL) or as a concentration (mg/mL, mcg/mL, units/mL). Weight is only needed for per-kg doses.
Dose → Rate: mL/hr = dose × weight (if per kg) × 60 (if per minute) ÷ concentration, after converting mcg ↔ mg and milliunits ↔ units.
Rate → Dose: dose = mL/hr × concentration ÷ weight (if per kg) ÷ 60 (if per minute).
Volume & Drip: mL/hr = volume ÷ hours; gtt/min = volume × drop factor ÷ minutes, with drops per 15 seconds for bedside counting.
Time: hours = volume ÷ mL/hr; add a start time to get the finish clock time.

Use cases

Program volumetric infusion pumps (mL/hr) for vasopressor, heparin, insulin or oxytocin orders.
Calculate gravity drip rates (drops/minute and drops/15 seconds) when electronic pumps are unavailable.
Back-calculate the delivered mcg/kg/min or units/hr dose from an existing pump setting as an independent check.
Find when an IV bag will run out for handover and bag-change planning.
Double-check clinical math for nursing pharmacology and dosage calculation examinations.

Frequently Asked Questions

Last updated: 2026-10-09 · Reviewed by Nham Vu