Lamb Cooking Time Chart (by weight)
Sear hot then reduce to 180°C. Lamb is best pink (60°C). Rest 15 min before carving.
| Weight | Pink / rare | Medium | Well done |
|---|---|---|---|
| 1 kg | 1 hr | 1 hr 15 min | 1 hr 30 min |
| 1.5 kg | 1 hr 20 min | 1 hr 40 min | 2 hr |
| 2 kg | 1 hr 40 min | 2 hr 5 min | 2 hr 30 min |
| 2.5 kg | 2 hr | 2 hr 30 min | 3 hr |
| 3 kg | 2 hr 20 min | 2 hr 55 min | 3 hr 30 min |
Lamb Cooking Times by Weight
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How This Calculator Works — Formula & Method
Source: standard UK roasting guidance · applied deterministically · verify with a thermometer
| Constant | Value | Source |
|---|---|---|
| Pink / rare — min per 500 g | 20 min (range 15–20) | UK roasting guides |
| Pink / rare — internal temp | 55°C / 131°F | FSA / thermometer |
| Medium — min per 500 g | 25 min (range 20–25) | UK roasting guides |
| Medium — internal temp | 60°C / 140°F | FSA / thermometer |
| Well done — min per 500 g | 30 min (range 25–30) | UK roasting guides |
| Well done — internal temp | 70°C / 158°F | FSA / thermometer |
| Base offset | 25 min | Standard |
| Oven | 220°C sear for 20 min, then 180°C | Method |
| Resting | 15 min | Best practice |
— Lamb cooking time —
total_min = min_per_500g × (weight_g / 500) + base_offset
range = [lo_per_500g … hi_per_500g] × (weight_g / 500) + base_offset
conventional_oven = fan_temp + 10–20°C (same time)
fahrenheit = derived table from °C
— algorithm —
lookup(meat, cut, doneness) → point_estimate → guidance_range
→ internal_target_temp → verify_with_thermometer()
total_min = min_per_500g × (weight_g / 500) + base_offset
range = [lo_per_500g … hi_per_500g] × (weight_g / 500) + base_offset
conventional_oven = fan_temp + 10–20°C (same time)
fahrenheit = derived table from °C
— algorithm —
lookup(meat, cut, doneness) → point_estimate → guidance_range
→ internal_target_temp → verify_with_thermometer()
Public roasting guidance applied deterministically — this is not a food-safety authority. Always cook to the stated internal temperature, measured with a meat thermometer.
Frequently Asked Questions
About 50 minutes per kg for medium (40/kg rare, 60/kg well done), plus a base of 25 minutes, in a fan oven at 180°C.
Lamb internal temperatures: Pink / rare 55°C, Medium 60°C, Well done 70°C. Measure with a meat thermometer.
Yes. A fan oven runs about 20°C hotter than conventional — use 180°C fan (190°C conventional) for the times shown. Sear hot then reduce to 180°C. Lamb is best pink (60°C). Rest 15 min before carving.