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 |
|---|---|---|---|
| 3 lb | 1 hr 14 min | 1 hr 33 min | 1 hr 52 min |
| 4 lb | 1 hr 33 min | 1 hr 56 min | 2 hr 19 min |
| 5 lb | 1 hr 51 min | 2 hr 18 min | 2 hr 46 min |
| 6 lb | 2 hr 9 min | 2 hr 41 min | 3 hr 13 min |
| 7 lb | 2 hr 27 min | 3 hr 4 min | 3 hr 41 min |
Lamb Cooking Times by Weight
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How This Calculator Works — Formula & Method
Source: standard US roasting guidance · applied deterministically · verify with a thermometer
| Constant | Value | Source |
|---|---|---|
| Pink / rare — time per lb | 18 min/lb (range 15–20/500 g) | US roasting guides |
| Pink / rare — internal temp | 131°F / 55°C | USDA / thermometer |
| Medium — time per lb | 23 min/lb (range 20–25/500 g) | US roasting guides |
| Medium — internal temp | 140°F / 60°C | USDA / thermometer |
| Well done — time per lb | 27 min/lb (range 25–30/500 g) | US roasting guides |
| Well done — internal temp | 158°F / 70°C | USDA / thermometer |
| Base offset | 25 min | Standard |
| Oven | 430°F sear for 20 min, then 350°F | Method |
| Resting | 15 min | Best practice |
— Lamb cooking time —
total_min = min_per_500g × (weight_lb × 453.592 / 500) + base_offset
range = [lo_per_500g … hi_per_500g] × (weight / 500) + base_offset
conventional_oven = fan_temp + 10–20°C (same time)
celsius = derived table from °F
— algorithm —
lookup(meat, cut, doneness) → point_estimate → guidance_range
→ internal_target_temp → verify_with_thermometer()
total_min = min_per_500g × (weight_lb × 453.592 / 500) + base_offset
range = [lo_per_500g … hi_per_500g] × (weight / 500) + base_offset
conventional_oven = fan_temp + 10–20°C (same time)
celsius = derived table from °F
— 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 23 minutes per lb for medium (18/lb rare, 27/lb well done), plus a base of 25 minutes, at 350°F.
Lamb internal temperatures: Pink / rare 131°F, Medium 140°F, Well done 158°F. Measure with a meat thermometer.
Yes. A fan (convection) oven runs about 20°C / 35°F hotter than conventional — use 350°F / 180°C for the times shown. Sear hot then reduce to 180°C. Lamb is best pink (60°C). Rest 15 min before carving.
🇬🇧 Cooking in kg & °C? Use the UK lamb calculator →