U-100 pen conversion formula
Dial units = amount in mg ÷ concentration in mg/mL × 100
The first division gives the liquid volume in mL. Multiplying by 100 converts that volume to the U-100 scale. The calculation must then be checked against your pen’s increment and dial limit.
Example: 1 mg from a 5 mg/mL solution
1 ÷ 5 = 0.2 mL. On a U-100 scale, 0.2 × 100 = 20 units. On the illustrated 1-unit-increment, 60-unit-maximum pen, 20 is an exact dial setting. This example does not determine an appropriate dose.
What happens if the result falls between dial marks?
For example, 0.125 mg ÷ 5 mg/mL × 100 = 2.5 units. A pen that moves only in 1-unit increments cannot represent 2.5 exactly. PeppyCalc flags that mismatch and does not round to another amount.
What if the result exceeds the pen’s maximum?
The tool flags a result above the dial limit you entered. It does not automatically split the amount into multiple administrations or recommend changing the concentration.
Are pen units the same as mg or clicks?
No. This tool uses the U-100 volume relationship: 100 units per mL. Milligrams depend on concentration. A manufacturer’s click count is a separate mechanism and is not established by this formula. Biological activity units (IU) also require product-specific information.
Need the full calculation and a printed report?
Use the full peptide reconstitution calculator, choose the matching U-100 injection-pen option, and save the result. Saved calculations can be included in a report or printed as vial labels.