Roast chicken: 45 min/kg plus 20 min at 75°C

Roasting a chicken to the right doneness is about matching weight to time and always finishing by checking the internal temperature. For a typical 1.5 kg chicken, that means about 1 hour 28 minutes in the oven, but the real test is reaching a safe 75 °C (167 °F) at the thickest part.

Roasting time by weight: the 45 min/kg plus 20 min rule

Many home cooks start with a simple, time-tested formula for roasting a whole chicken: 45 minutes per kilogram, plus an extra 20 minutes at the end. You’ll see this approach in countless home kitchen guides and classic recipes—whether you’re aiming for a straightforward Sunday roast or a Bavarian-style Hendl for a festival table[1].

To put it into practice:

• Weigh your chicken in kilograms.
• Multiply that weight by 45 to get the base roasting time in minutes.
• Add 20 minutes to account for thorough cooking at the joints and cavity.

For example, say you have a 1.5 kg chicken:

• 1.5 kg × 45 min/kg = 67.5 min
• 67.5 min + 20 min = 87.5 min total roasting time

This method isn’t pinned to a single scientific authority, but it has stood up in kitchens worldwide for reliably turning out roast chicken that’s cooked through without drying out. It’s a practical baseline—especially useful when you’re adapting recipes for larger or smaller birds.

Why internal temperature is the real test of doneness

Cooking time gives you a ballpark, but internal temperature is your only guarantee the chicken is safe to eat. Use a meat thermometer: insert the probe into the thickest part of the thigh, keeping clear of bone, which heats faster than the meat and can throw off your reading[2].

Thermometers—whether single or multi-probe—let you track the temperature where it counts. This matters because ovens run hot or cold, chickens vary in size, and only a thermometer shows when the inside reaches the temperature needed to kill harmful bacteria[2].

Source 2 notes that poultry should reach 74 °C (165 °F) before it is safe to consume, and if the bird is stuffed, the stuffing’s center should also reach about the same temperature. Rely on your thermometer for both spots.

Meat thermometers come in digital and dial styles, but avoid pop-up timers or bimetal coil types as your only check; source 2 points out they are the least reliable. For the most consistent results, use an electronic probe thermometer and take the reading with the chicken still in the oven, holding the tip in the middle of the meat, away from any bone[2].

A worked example: Roasting a 1.5 kg chicken

Suppose you’re roasting a typical 1.5 kg chicken for dinner. Here’s how you’d apply the formula and check doneness:

1. Calculate roasting time:

1.5 kg × 45 min/kg = 67.5 min 67.5 min + 20 min = 87.5 min

1. Prepare and roast:

Season and truss the chicken as you like. Roast in a preheated oven at your chosen temperature (most home recipes use 180–200 °C/350–400 °F).

1. Check temperature:

About 10 minutes before the calculated time is up, insert a meat thermometer into the thickest part of the thigh, not touching bone.

1. Finish when ready:

If the thermometer reads 75 °C (167 °F) or above, the chicken is done. If not, return it to the oven and check again after 5–10 minutes.

1. Rest before carving:

Let the chicken rest out of the oven for 10–15 minutes before carving. This helps juices redistribute and makes for easier slicing.

Common mistakes and how to avoid them

Even experienced cooks can run into pitfalls with roast chicken. Here’s what to watch for:

• Relying on time alone:

Ovens can run hot or cold, and chickens vary in shape. Always check with a thermometer to avoid undercooked or dry results[2].

• Measuring temperature at the wrong spot:

The thickest part of the thigh, not touching bone, is the standard. Checking only the breast can give a false sense of doneness, as dark meat cooks slower[2].

• Skipping the rest:

Carving straight from the oven lets juices run out, leading to dry meat. Always rest the chicken before serving.

• Wrong oven temperature:

Roasting too hot can burn the skin before the inside cooks; too low and the skin won’t crisp. Stick to 180–200 °C (350–400 °F) unless your recipe says otherwise.

Internal temperature: why 75 °C (167 °F) is the standard

Food safety guidance, as summarized in the Wikipedia entry on meat thermometers, points to 74 °C (165 °F) as the temperature poultry must reach internally for safety[2]. This is the figure that kills common pathogens in poultry. If the bird is stuffed, the same 74 °C (165 °F) applies—measured at the center of the stuffing, not just the meat[2].

Most home thermometers and many digital models are designed to alert or display when this temperature is reached, so it’s practical to rely on this reading. If you regularly roast whole birds, consider using a multiprobe thermometer: single-probe models only give you one point in the bird, while a multiprobe setup lets you check both thigh and breast (or stuffing), catching uneven cooking or cool spots[2].

The Wikipedia source does not specify a higher temperature for dark or white meat, nor does it offer a margin above 74 °C (165 °F). For cooks looking for juicier breast meat at a lower temperature, be aware that this is not reflected in standard food safety guidelines—hitting the 74 °C (165 °F) mark is the published, tested target for doneness.

Questions readers ask

How do I convert roasting times for pounds?

Multiply the chicken’s weight in pounds by 20 minutes per pound, then add 20 minutes. For example, a 4 lb chicken: 4 × 20 = 80, plus 20 = 100 minutes.

Is it safe to roast chicken without a thermometer?

It’s not recommended. Color and juices are unreliable. Only a thermometer confirms the chicken has reached a safe internal temperature[2].

What if my chicken is larger or smaller than 1.5 kg?

Use the same formula: 45 minutes per kilogram plus 20 minutes. Adjust the total time, but always check doneness with a thermometer.

How the numbers work

Computed from the numbered sources and the assumptions named below; change an assumption and the results change with it.

Sources

1. Roast chicken - Wikipedia
2. Meat thermometer - Wikipedia