Prime Rib Calculator for Holiday Dinners
Enter guests and dinner time. You get the roast to order, smoke time and when to light the smoker.
A standing rib roast is the classic Christmas and New Year's Eve dinner. Order it from the butcher at least a week ahead.
| Ask the butcher for | 4-rib roast |
| Raw weight, bone in | 8 lb |
| Cooked meat to carve (62.5% USDA yield) | 5 lb |
| Rest before carving | 20–30 min |
Dinner-day timeline
| Time | Step |
|---|---|
| 10:25 am | Light the smoker and settle it at 225°F |
| 11:10 am | Roast on the smoker, fat side up, probe in the center |
| 3:50 pm | Start checking: pull at 130°F for medium rare |
| 4:30 pm | Latest pull time, then rest it loosely tented |
| 5:00 pm | Carve and serve |
The night before, salt the roast all over and leave it uncovered in the fridge. Go by the thermometer, not the clock: the time range is a planning estimate.
Prime rib by guest count
Bone-in roast, 8 oz of cooked meat per guest, smoked to 130°F in the center.
| Party | Raw weight | Ribs | Smoke at 225°F | Smoke at 250°F |
|---|---|---|---|---|
| 4 guests | 3.5 lb | 2 | 2.05–2.35 h | 1.75–2.05 h |
| 6 guests | 5 lb | 3 | 2.9–3.35 h | 2.5–2.9 h |
| 8 guests | 6.5 lb | 4 | 3.75–4.35 h | 3.25–3.75 h |
| 10 guests | 8 lb | 4 | 4.65–5.35 h | 4–4.65 h |
| 12 guests | 10 lb | 5 | 5.8–6.7 h | 5–5.8 h |
| 16 guests | 13 lb | 7 | 7.55–8.7 h | 6.5–7.55 h |
| 20 guests | 16 lb | 8 (2 roasts) | 4.65–5.35 h | 4–4.65 h |
How much prime rib per person
Bone and trim are about 38% of a bone-in rib roast (USDA Food Buying Guide), so each cooked ounce on the plate takes about 1.6 oz raw. For 10 guests:
| Cooked portion | Good for | Raw bone-in | Ribs |
|---|---|---|---|
| 6 oz | light, with plenty of sides | 6 lb | 3 |
| 8 oz | standard holiday dinner | 8 lb | 4 |
| 10 oz | generous | 10 lb | 5 |
| 12 oz | steakhouse cut | 12 lb | 6 |
Doneness and safety
- Pull at 130°F for medium rare. The center climbs a few degrees during the rest. Pull at 120–125°F for rare, 135–140°F for medium.
- USDA guideline: the safe minimum for whole beef roasts is 145°F with a 3-minute rest. Medium rare is below that guideline; serve it to healthy adults who choose it, and cook to 145°F for anyone pregnant, very young, elderly or immune-compromised.
- Leftovers: refrigerate within 2 hours, eat within 3–4 days, reheat slices gently to 165°F or serve them cold.
How we calculate
- Raw weight = guests × cooked ounces per guest ÷ 16 ÷ 0.625 (USDA cooked yield for bone-in rib roast), rounded up to the next half pound.
- Ribs: about 2 lb per rib bone (a butcher's rule of thumb, our estimate), at least 2 ribs; more than 7 ribs is split into separate roasts that smoke side by side.
- Smoke time per pound and rest come from our smoke time data for prime rib; the timeline puts the roast on at the long end of the range, so a fast cook just rests longer.
- Smoker preheat: 45 minutes (our estimate).
| Factor | Value | Source |
|---|---|---|
| Cooked yield, bone-in rib roast | 62.5% | USDA Food Buying Guide |
| Smoke rate and pull temperature | 130°F | Traeger smoked prime rib guide |
Data as of Oct 2026. Full list of sources: How we calculate.
Plan the rest
FAQ
How much prime rib per person?
Plan 8 oz of cooked meat per guest for a holiday dinner with sides. With bone and trim that is about 0.8 lb of bone-in roast per person, or 1 rib for every 2 guests.
How big a prime rib for 10 people?
About 8 lb bone-in, a 4-rib roast, for 8 oz cooked per guest.
How many ribs for 8 people?
A 4-rib roast of about 6.5 lb.
How long to smoke a prime rib at 225°F?
Roughly 35–40 minutes per pound to 130°F in the center: about 4.65–5.35 hours for an 8 lb roast, then rest 20–30 minutes.
When should I put the prime rib on for a 5 pm dinner?
For an 8 lb roast at 225°F, put it on at about 11:10 am and light the smoker 45 minutes before that. Use the calculator for your weight and dinner time.