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🧫 Mobile Phase Mixing Ratio Calculator

Calculate the exact volume of each solvent needed to prepare a mobile phase at a given mixing ratio.

Ratio (parts) — leave a solvent at 0 if using only 2 components:

Solvent A ratio e.g. 70

Solvent B ratio e.g. 30

Solvent C ratio optional

Total Mobile Phase Volume Needed mL

Volumes to Mix

💡 Note: This calculates volume ratios only (v/v), not accounting for volume contraction on mixing (common with water/organic mixtures). For high-precision work, prepare each solvent volumetrically and mix, or use volumetric mixing pumps rather than premixing by volume.

📖 Example: Mobile phase 70:30 (A:B), total 1000 mL: Volume A = 1000×(70/100) = 700 mL; Volume B = 1000×(30/100) = 300 mL.

Frequently asked questions

Does this account for volume contraction when mixing solvents?

No — this calculator computes simple volume ratios (v/v), which is the standard way HPLC mobile phases are specified. It does not correct for the slight volume contraction that occurs when mixing some solvent pairs (e.g. water and methanol), which is a separate consideration for very high-precision work.

Can I use this for ternary (3-solvent) mobile phases?

Yes — enter a ratio for Solvent C in addition to A and B, and the calculator will scale all three proportionally to your total volume.

Should I premix by volume or use the instrument's pump to mix in real time?

Both approaches are common. Premixing (isocratic mobile phase in one bottle) is simple and this calculator directly supports it. Many modern HPLC systems can also mix solvents from separate reservoirs in real time via the pump, which avoids the need to premix but requires the pump's mixing ratios to be set correctly instead.

Accuracy & how this is derived

Derivation: Direct proportional scaling: each solvent's volume equals the total mobile phase volume multiplied by that solvent's share of the total ratio parts.

Validated against: Basic proportional arithmetic — standard practice for isocratic mobile phase preparation described in HPLC method development references.

⚠️ For educational and research support only — verify critical results independently before use in regulated, clinical, or publication-bound work.

✔ Last updated: July 2026 · Report an error

Preparing HPLC mobile phases from mixing ratios

HPLC mobile phases are commonly specified as volume ratios, such as 70:30 water to acetonitrile, which describe the relative proportion of each solvent rather than absolute volumes. Converting a ratio into the actual volume of each component needed for a given total batch size is a simple proportional calculation, but errors here directly affect retention times and selectivity, making an accurate mixing calculation an important step in reproducible method execution.