IV Drip Rate Calculator (gtt/min and mL/h)

Work out the drops per minute for an infusion from the volume, the time, and the giving set's drop factor — or the time a set rate will take.

Drip rate–

Count over 15 seconds–

Pump rate–

Infusion time–

A reference conversion, not a prescription. Always check the order, the pump, and the set against local policy.

Drip rate reference table

Drops per minute for common bag sizes and durations, at each of the four standard drop factors. A 1000 mL bag over 8 hours runs at125 mL/h — about31 drops a minute through a 15 gtt/mL set.

Volume	Over	mL/h	10 gtt/mL	15 gtt/mL	20 gtt/mL	60 gtt/mL
1000 mL	8 h	125	20.83	31.25	41.67	125
1000 mL	12 h	83.33	13.89	20.83	27.78	83.33
1000 mL	4 h	250	41.67	62.5	83.33	250
500 mL	8 h	62.5	10.42	15.63	20.83	62.5
500 mL	4 h	125	20.83	31.25	41.67	125
500 mL	2 h	250	41.67	62.5	83.33	250
250 mL	2 h	125	20.83	31.25	41.67	125
250 mL	1 h	250	41.67	62.5	83.33	250
100 mL	1 h	100	16.67	25	33.33	100
100 mL	30 min	200	33.33	50	66.67	200

Rates are drops per minute (gtt/min), unrounded.

How an IV drip rate is worked out

This is a general-information calculator, not medical advice, and not a substitute for a prescription or local protocol. It converts between volume, time, and drops; it does not decide what a patient should receive.

When an infusion runs by gravity rather than through a pump, the flow is set by counting drops in the chamber. Every giving set is manufactured to deliver a fixed number of drops per millilitre — its drop factor, written on the packaging in gtt/mL. Once you know that number, the rest is arithmetic.

gtt/min = (volume in mL × drop factor) / time in minutes

Adult macrodrip sets are usually 10, 15, or 20 gtt/mL. Microdrip (or "paediatric") sets are 60 gtt/mL, which gives finer control over small volumes and has a convenient property: at 60 gtt/mL the drip rate in gtt/min is numerically identical to the flow rate in mL/h, so no conversion is needed at all.

Worked example

One litre over eight hours through a 15 gtt/mL set: 8 hours is 480 minutes, so the rate is (1000 × 15) / 480 = 31.25 drops per minute. In practice you'd set it to 31, and confirm by counting about 8 drops in 15 seconds rather than standing there for a full minute. Expressed for a pump, the same infusion is 1000 / 8 = 125 mL/h.

Why the drop factor matters so much

The drop factor is the one number people get wrong, and it changes the answer by a factor of six across the range of available sets. That same litre over eight hours is about 21 drops a minute on a 10 gtt/mL set, 31 on a 15, 42 on a 20, and 125 on a microdrip. Read it off the packet rather than assuming — the flow rate in mL/h is unchanged, but the count you're aiming for is not.

Rounding and drift

You cannot deliver a quarter of a drop, so the set rate is always rounded to a whole number and the infusion finishes slightly early or late. Gravity infusions also slow as the bag empties and the pressure head falls, which is why they're re-checked rather than set once. For anything where the exact rate matters, a volumetric pump programmed in mL/h is used instead.

For converting the volumes themselves, see thevolume converter; for the time arithmetic on its own, the time converter.