What is the formula behind sous vide time calculations?

Two independent constraints combine. First, pasteurisation time: how long the food must stay at the target temperature to achieve a 6.5 D–7 D reduction in the relevant pathogen (Salmonella for poultry, E. coli O157:H7 for beef, Trichinella for pork) — values from USDA FSIS tables and Douglas Baldwin's guide. Second, heat-penetration time: the time for the thermal centre of a slab of thickness d to reach equilibrium, modelled as t ≈ (d/2)² × Fo / α, where α ≈ 1.4 × 10⁻⁷ m²/s is the thermal diffusivity of raw muscle tissue and Fo = 0.4 is a conservative Fourier number for 99.9% equilibration. The total minimum time is the sum of both.

Why does a thicker piece of meat take longer?

The inside of the meat must actually reach the bath temperature before pasteurisation begins. Heat travels through meat by conduction at roughly 1.4 × 10⁻⁷ m²/s — a 40 mm slab has four times the penetration time of a 20 mm slab because the thermal-centre distance is squared in the formula. Slicing a roast in half before bagging it can cut cook time by more than 75 minutes.

Is sous vide chicken at 60°C actually safe?

Yes, if held long enough. Pasteurisation is a function of both temperature and time. At 60°C, USDA tables require chicken to be held for about 11 minutes at the centre to achieve a 7 D reduction in Salmonella — far safer than the common misconception that only 74°C (165°F) is safe. The traditional high-temperature rule achieves instantaneous pasteurisation; sous vide achieves the same log-reduction more slowly at lower temperatures, preserving moisture and texture.

Can I cook salmon below 60°C sous vide?

Only if the fish has been commercially frozen first. The FDA requires fish intended for raw or partially cooked consumption to be frozen at −20°C for 7 days (or −35°C for 15 hours) to kill Anisakis parasites. Commercial sushi-grade salmon is typically pre-frozen; supermarket fillets may not be. Above 60°C, parasites are destroyed by heat alone regardless of prior freezing.

What does the 'recommended window' mean?

The window is the range of total cook times that both guarantees pasteurisation and keeps texture at its best. Below the lower bound, the centre may not be pasteurised. Above the upper bound, the protein fibres break down further — chicken goes stringy, beef goes mushy. The window is derived from the texture tables in Baldwin's guide cross-checked against the pasteurisation minimum.

Should I add chilling time if I'm not eating immediately?

Yes. After the cook, transfer the sealed bag immediately to an ice-water bath (50% ice, 50% water) for at least 30 minutes per 25 mm of thickness before refrigerating. This rapidly brings the core below 3°C, re-entering the safe zone. The ice-bath time is not included in this calculator as it is temperature-independent — the physics of ice-water cooling are nearly identical regardless of bath temperature.

Sous Vide Time & Temperature Calculator

Sous vide (French: “under vacuum”) is the technique of sealing food in a bag and cooking it in a precisely temperature-controlled water bath. Because the bath temperature equals the desired core temperature, the food cannot overcook — it simply needs enough time for the heat to penetrate to the centre and for pasteurisation to complete. This calculator computes both constraints and gives you the earliest safe pull time plus the quality window.

How it works

The calculator combines two independent equations for each combination of protein and bath temperature.

1. Heat penetration — how long the thermal centre takes to reach the bath temperature. For a slab of thickness d (mm), the simplified infinite-slab conduction formula is:

t_heat (min) = (d/2)² × Fo / α / 60

where α ≈ 1.4 × 10⁻⁷ m²/s is the thermal diffusivity of raw muscle tissue and Fo = 0.4 is the Fourier number corresponding to 99.9% thermal equilibration at the centre. In practice this means a 30 mm chicken breast takes roughly 8 minutes to reach bath temperature; a 60 mm roast takes about 32 minutes.

2. Pasteurisation hold time — the minimum time the centre must stay at the bath temperature to achieve the target log-reduction in pathogens. Values are linearly interpolated from the USDA FSIS / Douglas Baldwin tables:

Poultry (chicken, duck): 7 D reduction in Salmonella — the most conservative target
Beef and lamb: 6.5 D reduction in E. coli O157:H7 and L. monocytogenes
Pork: 6.5 D reduction in Trichinella spiralis and Salmonella
Fish: FDA parasitic-destruction tables (Anisakis) — freeze first below 60°C
Eggs: USDA Salmonella enteritidis data for whole-egg pasteurisation
Vegetables: no pathogen concern — times are texture-only (pectin softening)

Total minimum = t_heat + t_pasteurisation. Remaining in the bath beyond the minimum (up to the texture-window upper bound) improves juiciness without adding food-safety risk.

Worked example

A 40 mm-thick chicken breast in a 63°C bath:

Heat penetration: (20 mm)² × 0.4 / (1.4 × 10⁻⁷ × 10⁶ × 60) ≈ 9 min
Pasteurisation hold at 63°C: 4 min (interpolated from USDA table)
Total minimum: 13 min — but the texture window is 1–2 hours
Pull any time between 1 h and 2 h for juicy, fully white, pasteurised chicken

Food	Temp	Thickness	Minimum	Quality window
Chicken breast	63°C	30 mm	11 min	1–2 h
Beef steak (medium-rare)	54°C	40 mm	19 min	1–3 h
Salmon	50°C	25 mm	7.5 h*	15–60 min*
Pork loin	60°C	35 mm	5.5 h	1.5–3 h
Duck breast	57°C	30 mm	34 h	1.5–3 h

*Salmon at 50°C requires the fish to have been commercially frozen first (FDA advisory).

Formula note

The pasteurisation tables use the D-value / z-value model: each 10°C (18°F) rise in temperature reduces the D-value (time to achieve one log-reduction) by a factor of 10^(10/z), where z ≈ 6–8°C for most foodborne pathogens. This means a 3°C drop in bath temperature can multiply the required hold time by 2–4×. The calculator uses direct table lookup with linear interpolation rather than re-deriving the z-value, to stay close to the regulator-approved figures.