Osmolality & Tonicity Helper
Sum ideal osmolarity by ingredient and calculate helper dilution or solute adjustments from measured osmolality.
With a measured value, the adjustment basis is mOsm/kg; otherwise it is ideal mOsm/L. They are not directly converted. Enter all three adjustment-solute values together.
Osmotic calculation results
Enter ingredients and current volume.
The ideal value assumes complete dissolution, additivity, and the entered particle factor and φ. Osmolarity (mOsm/L), osmolality (mOsm/kg), and tonicity are not equivalent; tonicity depends on membrane permeability and biologically effective osmoles. Confirm product suitability with validated osmolality measurement and product-specific specifications and use evidence.
Basis: ideal van’t Hoff particle summation and the USP <785>/<1785> distinction among osmolality, osmolarity, tonicity, and nonideal behavior.
Tool Guide
Definition
Osmolality & Tonicity Helper — Sums ideal osmolarity contributions from each ingredient’s mass concentration, MW, particle factor, and osmotic coefficient. An optional measured osmolality remains a separate adjustment basis for theoretical dilution or user-defined adjustment-solute mass.
Purpose
(1) Sum ideal mOsm/L for a multicomponent formulation, (2) trace ingredient contributions, (3) record measured mOsm/kg separately from the estimate, and (4) calculate theoretical dilution or solute adjustment toward a target.
How to Use
① Enter each solute’s g/L (numerically equal to mg/mL), MW, effective particle factor i, and φ. ② Enter current solution volume. ③ If available, enter measured osmolality in mOsm/kg; adjustment uses it as the preferred basis. ④ Optionally enter a target plus MW/i/φ for a low-value adjustment solute. The tool neither converts among osmolarity, osmolality, and tonicity nor makes an automatic suitability decision.
Examples
Example) NaCl 5.844 g/L with MW 58.44, i=2, φ=1 contributes 200 mOsm/L; glucose 18.016 g/L with MW 180.16 and i=1 contributes 100 mOsm/L, totaling 300 mOsm/L. Raising 1 L ideally to 320 with NaCl requires about 0.5844 g. Confirm the actual value by measurement.