Pharmaceutics

Sterile Dose Volume Calculator

Works out how much of a sterile solution to draw up for a dose, and the concentration after dilution.

Volume to administer

2.00mL

Volume within typical administration range

Dose and strength

Desired dose

The prescribed dose, in the same amount unit as the concentration.

Concentration

Concentration = amount of drug per mL (from the vial label)

Show volume in

1 mL = 1000 μL; 1 L = 1000 mL.

Total dilution volume (optional)

Enter if you want to calculate final concentration

Try an example

Working

The numbers you entered, plugged into the formula.

Volume = 500 ÷ 250 mg/mL2mL

Volume check

Volume within typical administration range. Guide: 0.1 - 10 mL typical range · < 0.1 mL use insulin syringe · > 50 mL review dose.

Administration guidelines

Small volumes (< 1 mL)

Use insulin syringes for accuracy

Minimum measurable volume: 0.01 mL

Consider dead space in syringe

Ideal for subcutaneous injections

Medium volumes (1-10 mL)

Use standard 3-10 mL syringes

Suitable for IM injections

Check muscle size for IM administration

Divide large volumes between sites if needed

Large volumes (> 10 mL)

Typically for IV infusion

Use appropriate IV bags/syringes

Consider infusion rate and time

Check for compatibility with diluent

Volume = Desired Dose ÷ Concentration

% (w/v): concentration in mg/mL = (% ÷ 100) × 1000

Final concentration = Desired Dose ÷ Total dilution volume

Example: 500 mg from a 250 mg/mL vial is 500 ÷ 250 = 2 mL. A 2% (w/v) solution holds 2 g in 100 mL, i.e. 20 mg/mL, so 50 mg needs 50 ÷ 20 = 2.5 mL.

Volumes under 0.1 are shown to 3 decimals, everything else to 2. The volume check uses the figure in the unit you chose.

Guide: Pharmaceutical Dose Calculations: Units, Body Weight and Body Surface AreaThe concept in full, with practice questions.Reconstitution & IV Compounding CalculatorWhen the vial is a powder, work out the concentration after reconstitution first.

References

Stockton SJ. Stoklosa and Ansel's Pharmaceutical Calculations. 16th ed. Philadelphia: Wolters Kluwer; 2021.

Common questions

Convert one of them first so both use the same amount unit (1 mg = 1000 mcg), or pick the matching concentration unit. The calculator divides the two numbers as entered and does not convert between mg, mcg, g and units.

A w/v percentage is grams per 100 mL, so 1% is 10 mg/mL. The calculator converts the percentage to mg/mL and divides your dose (in mg) by it.

The check compares the displayed number with its bands (below 0.1, above 10). 2 mL shown as 2000 μL is flagged as large, and 500 mL shown as 0.5 L is flagged as typical — judge the volume in mL.

When a dose is added to a bag or syringe of diluent, the final concentration (dose ÷ total volume) is what goes on the label and what infusion rates are calculated from.

Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy