Novis
Novis / Free tools / IV drip rate

IV drip rate and dosage calculator

Practice the nursing math: drops per minute for gravity tubing, the pump rate in mL/hr, and a dose by weight with the volume to draw up. Every step shows the units cancelling, the way dimensional analysis is taught.

For practice only. This is a study tool for learning dosage calculation. Do not use it to set a real infusion or calculate a dose for a patient. Follow your instructor's rounding rules and your facility's policies.

On the tubing label: 10, 15, 20 or 60

    The drip rate formula

    gtt/min = volume (mL) x drop factor (gtt/mL) / time (min)

    The drop factor is how many drops of that tubing make one mL. Macrodrip sets are usually 10, 15 or 20 gtt/mL; microdrip sets are 60 gtt/mL. Multiplying mL by gtt/mL cancels the mL and leaves drops, and dividing by minutes leaves drops per minute.

    A pump does not count drops. It is set in mL/hr, so the pump rate is simply the volume divided by the time in hours.

    Worked examples

    1000 mL over 8 hours with 15 gtt/mL tubing

    1. Time in minutes: 8 hr x 60 min/hr = 480 min.
    2. Total drops: 1000 mL x 15 gtt/mL = 15,000 gtt.
    3. Drops per minute: 15,000 gtt / 480 min = 31.25 gtt/min.
    4. Round to a whole drop: 31 gtt/min. On a pump, the same order is 1000 mL / 8 hr = 125 mL/hr.

    5 mg/kg for a 154 lb patient, stock 250 mg in 5 mL

    1. Pounds to kilograms: 154 lb / 2.2 lb per kg = 70 kg.
    2. Dose: 5 mg/kg x 70 kg = 350 mg.
    3. Stock strength: 250 mg / 5 mL = 50 mg/mL.
    4. Volume: 350 mg x 1 mL / 50 mg = 7 mL, written as 7.0 mL.

    Mistakes that cost points

    Leaving the time in hoursThe drip rate is per minute. Multiply hours by 60 before dividing, or the answer is 60 times too big.
    Forgetting the drop factormL per minute is not drops per minute. Multiply by the gtt/mL on the tubing.
    Multiplying by 2.2 instead of dividingA weight in kg is always a smaller number than the same weight in lb. 154 lb is 70 kg, not 339.
    Rounding too earlyKeep the full numbers until the last step, then round once, the way your course asks.

    Practice problems

    Infuse 1000 mL over 8 hr with 15 gtt/mL tubing. How many gtt/min?
    1000 x 15 / 480 = 31.25, so 31 gtt/min.
    Infuse 100 mL over 30 min with 20 gtt/mL tubing. How many gtt/min?
    100 x 20 / 30 = 66.7, so 67 gtt/min.
    The order is 125 mL/hr and the tubing is 60 gtt/mL. How many gtt/min?
    125 x 60 / 60 = 125 gtt/min. With microdrip tubing, gtt/min equals mL/hr.
    Infuse 250 mL over 1 hr 30 min on a pump. What rate?
    250 / 1.5 = 166.7 mL/hr.
    Order 5 mg/kg for a 154 lb patient. Stock is 250 mg in 5 mL. How many mL?
    154 / 2.2 = 70 kg, 5 x 70 = 350 mg, 350 / 50 = 7.0 mL.
    Order 15 mg/kg for a 20 kg child. Stock is 160 mg in 5 mL. How many mL?
    15 x 20 = 300 mg, 160 / 5 = 32 mg/mL, 300 / 32 = 9.375, so 9.4 mL.

    Practice it until it sticks

    Novis turns problems like these into a spaced-repetition deck, checks your own written work one step at a time, and tells you which step went wrong. Novis opens October 20.

    Join the waitlistMore free tools

    Related tools

    Henderson-Hasselbalch calculatorBuffer pH, pKa, the ratio for a target pH, fraction ionized, and the pH after adding HCl or NaOH. Isoelectric point (pI) and peptide charge calculatorpI and net charge of any short peptide, group by group. Michaelis-Menten and Lineweaver-Burk calculatorSolve for v, Km, Vmax or [S], and fit a Lineweaver-Burk plot from data.