Basic medication dose conversion and calculation are essential skills for those entering the nursing or pharmacology fields. There are three different methods for dosage calculation:
This page contains resources and examples for each of these calculation methods.
When performing calculations, do not round until calculating the final answer. Dosages of oral liquid medications for adults are typically rounded to the tenth for doses over 1 mL. For doses less than 1 mL the dosage is rounded to the hundredth.
For pediatric patients, it is important to be as precise as possible to avoid medication errors. Oral liquid medications less than 1 mL should be rounded to the hundredth.
When rounding, it is also important to use critical thinking to evaluate your final answer. For example, a drop cannot be administered as a fraction of a drop, so drops are rounded to the nearest whole number
Mass:
mcg → mg → g → kg ( ÷ by 1,000 )
lb → kg ( ÷ by 2.2 )
Volume:
mcL → mL → L → kL ( ÷ by 1,000 )
Time:
min → hr ( ÷ by 60 )
TO CONVERT  TO  YOU MUST 
ounces  grams  multiply by 28.3495 
ounces  kilograms  divide by 35.274 
pounds  grams  multiply by 453.592 
pounds  kilograms  divide by 2.205 
milliliters  tablespoon  divide by 15 
liter  fluid ounce  multiply by 33.814 
liter  cup  multiply by 4.167 
liter  gallon  divide by 3.78541178 
kilograms  pounds  multiply by 2.205 
KILO to BASE UNIT: Multiply by 1,000
KILO to CENTI: Multiply by 100,000
KILO to MILLI: Multiply by 1,000,000
KILO to MICRO: Multiply by 1,000,000,000
BASE UNIT to CENTI: Multiply by 100
BASE UNIT to MILLI: Multiply by 1,000
BASE UNIT to MICRO: Multiply by 1,000,000
CENTI to MILLI: Multiply by 10
CENTI to MICRO: Multiply by 10,000
MILLI to MICRO: Multiply by 1,000
MICRO to KILO: Divide by 1,000,000,000
MICRO to BASE UNIT: Divide by 1,000,000
MICRO to CENTI: Divide by 10,000
MICRO to MILLI: Divide by 1,000
MILLI to KILO: Divide by 1,000,000
MILLI to BASE UNIT: Divide by 1,000
MILLI to CENTI: Divide by 10
The metric system is a system of measurement that uses the meter, liter, and gram as base units of length (distance), capacity (volume), and weight (mass) respectively.
LENGTH  Meter (m) 
MASS  Gram (g) 
VOLUME  Liter (L) 
Metric system prefixes tell you how much bigger or smaller a unit is than the base unit. These prefixes are all powers of 10, which makes converting from one metric measurement to another very simple. Here are some common prefixes.
KILO: 1,000 × Base
HECTO: 100 × Base
DECA: 10 × Base
[BASE]
DECI: 0.1 × Base
CENTI: 0.01 × Base
MILLI: 0.001 × Base
MICRO: 0.000001 × Base
D/H x Q → (desired or dose/have) x quantity
mL/hr → milliliters per hour
gtt/min → drop(s) per minute
Nifty note: A drop is abbreviated gtt, with gtts used for the plural, and is often seen on prescriptions. These abbreviations come from gutta (plural guttae), the Latin word for drop.
mg/kg/day → milligrams per kilogram [of body weight] per day
gtts/mL→ also known as the drop factor: the number of drops it takes to make up one mL of fluid
D→ Dextrose
W → Water
S → Saline
NS → Normal Saline (0.9%NaCI)
RL → Lactated Ringer's
PO → per os or by mouth
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