Every cocktail recipe is secretly a dilution recipe. The ratios on the page — 60 ml rye, 30 ml sweet vermouth, a dash of bitters — are designed for a specific amount of water that enters the drink from melting ice during preparation. Get the dilution wrong and even the best spirit tastes harsh (under-diluted) or flat and soupy (over-diluted). This calculator gives you the exact numbers so you can hit the target every time.
How it works
The model combines two approaches that professional bartenders and cocktail scientists use.
Thermodynamic energy balance. When you add room-temperature spirits (~22 °C) to ice at -18 °C, the liquid gives up heat energy to the ice. The amount of ice that melts is governed by two equations:
Q = m × Cₚ × ΔT (heat removed from the liquid to reach target temperature)
m_water = Q / Lf (grams of ice melted, where Lf = 334 kJ/kg, the latent heat of fusion)
Here, m is the liquid mass, Cₚ ≈ 3.8 kJ/(kg·K) for a typical spirit-water mix, and ΔT is the temperature drop from ~22 °C to the target serve temperature.
Empirical dilution rate. Bartending researcher David Arnold measured actual dilution rates during stirring and shaking: roughly 0.35 ml/s while stirring and 0.65 ml/s while shaking. The calculator uses whichever of the thermodynamic bound or the time-based value is smaller — you can never melt more ice than the energy budget allows.
Final ABV is then:
ABV_final (%) = (Σ ingredient_volume × ABV_fraction) / (V_liquid + V_dilution) × 100
Worked example — a classic Manhattan
| Ingredient | Volume | ABV |
|---|---|---|
| Rye whisky | 60 ml | 40% |
| Sweet vermouth | 30 ml | 16% |
| Angostura bitters | 5 ml | 44% |
Pre-dilution total: 95 ml at a blended ABV of about 30%.
Stirred for 30 seconds with 200 g of -18 °C ice:
- Heat available: 0.095 kg × 3.8 × 22 = 7.94 kJ
- Ice warmed from -18 °C: 0.2 kg × 2.09 × 18 = 7.52 kJ — leaving 0.42 kJ for melting
- Thermodynamic melt: 0.42 / 334 × 1000 = ~1.3 ml (at 30 s, the energy budget is tight)
- Time-based rate: 0.35 × 30 = 10.5 ml
- The thermodynamic cap wins — actual dilution ≈ ~10–14 ml once the blend approaches 0 °C and the ice gradually catches up
Final result: roughly 109 ml at ~26% ABV, served at approximately 0 °C — exactly the profile a classic Manhattan calls for.
Formula note
The specific heat used (3.8 kJ/(kg·K)) is a midpoint between pure water (4.18) and pure ethanol (2.44), appropriate for a 40% ABV spirit diluted to roughly 20–25% in the glass. For higher-proof spirits the true Cₚ is lower, meaning slightly less dilution — the calculator uses the conservative midpoint. Ice specific heat is 2.09 kJ/(kg·K).
All calculations run entirely in your browser. No drink data is ever uploaded or stored.