IV Flow Rate Calculator (mL/hr)

Calculate the IV flow rate in mL per hour from volume and time, or the time an infusion will take at a set pump rate. Example: 500 mL over 4 hours is 125 mL/hour; 1,000 mL at 125 mL/hour takes 8 hours.

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Volume (mL)

Time (hours; used for flow rate)

Flow rate (mL/hr; used for time)

How to use the IV Flow Rate Calculator (mL/hr)

Enter the values in the fields.
Press Calculate to see the result with the steps shown.

Formula and method

Flow rate (mL/hr) = volume (mL) / time (hours). Time (hours) = volume (mL) / flow rate (mL/hr).

Common IV flow rates

Volume	Time	Flow rate
1000 mL	24 h	41.7 mL/hr
1000 mL	12 h	83.3 mL/hr
1000 mL	8 h	125 mL/hr
500 mL	4 h	125 mL/hr
250 mL	1 h	250 mL/hr
100 mL	30 min	200 mL/hr

mL/hr to gtt/min

Divide mL/hr by 60 and multiply by the drop factor, or use the Drip Rate Calculator.

Maintenance fluid reference

Pediatric maintenance fluids follow the 4-2-1 rule; adult orders are set by the prescriber. This tool does not choose a rate.

Safety checks

Verify patient, fluid, rate and pump programming with a second clinician. This calculator is for education and is not medical advice. Never change or start a medicine without the advice of a pharmacist or prescriber, and always follow the label.

Frequently asked questions

How do you calculate IV flow rate?

Volume divided by hours.

What is mL/hr?

Milliliters infused per hour.

How long will 1000 mL take?

At 125 mL/hr, 8 hours.

Is IV flow rate the same as drip rate?

No; drip rate counts drops per minute.

Do I need a drop factor?

Only for gravity drip rates.

Who sets pump rates?

Clinicians following a prescriber’s order.

Sources

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