**Tips for Drug Calculations**

Ø Always convert everything to
the same units before solving the calculation.

Ø Complete work from left to
right.

Ø Follow the ‘one unit’ or by
proportion rule: what you do to one side of an equation, do the same to the
other side.

Ø Write out the calculation
clearly.

Ø Write down every step. Do not
take short cuts; you are more likely to make a mistake.

Ø If you are copying formulas from
a reference source, double-check your work.

Ø Try not to depend on your
calculator. Gestimate your answer, then if you make a
mistake on the calculator, you are more likely to know that an error has been
made.

Ø If you are in doubt about a
calculation, stop and get help.

Ø
When
administering intravenous (IV) infusions, you need to know: the flow rate,
infusion time, and total volume.

**Use the following equations:**

ü
flow rate (mL/hr) = total volume (mL) ÷ infusion time (hr)

ü
infusion time (hr) = total volume (mL) ÷ flow rate (mL/hr)

ü
total volume
(mL) = flow rate (mL/hr) × infusion time (hr)