What temperature should a fridge and freezer actually be?

Fridge: 0–5°C, with 4°C or below recommended. Freezer: −18°C. These are the figures used by food safety authorities in the UK, EU and US, and there is solid reasoning behind each.

Why 5°C for the fridge. The danger zone for bacterial growth is roughly 5°C to 63°C, where pathogens multiply rapidly. Below 5°C growth slows dramatically. Note that it slows rather than stops — refrigeration extends safe storage, it does not sterilise. Listeria in particular can still grow slowly at fridge temperatures, which is why some foods have short use-by dates regardless.

Why not colder? Below 0°C food freezes, damaging texture in salad, dairy and many vegetables.

Why −18°C for the freezer. At this temperature microbial growth stops entirely and enzyme activity that degrades quality slows to a near-halt. It is cold enough for long-term storage without the energy cost of going lower.

How to check. Do not trust the dial. Most fridge controls are numbered 1–7 with no relation to temperature, and they set compressor duty rather than a target. A cheap fridge thermometer is the only reliable method. Place it in the middle, not the door, and read it after several hours.

Temperature varies within the cabinet, which is worth using deliberately:

Coldest: the bottom shelf, above the salad drawer. Raw meat and fish go here — also so drips cannot contaminate anything below.

Warmest: the door, which is exposed to room air every time it opens. Milk in the door is a common mistake; it belongs on a shelf.

Salad drawers are slightly warmer and more humid by design.

Other factors: an overfull fridge blocks air circulation; a nearly empty freezer is less efficient than a full one; and leaving the door open is the largest single cause of temperature rise.