Guests
20
Cake
1/4 sheet
Food Cost
$63
Balloons
40
Birthday Party Plan
20 Guests
~$163 food & extras
Cake
1/4 sheet
Balloons
40
Goody Bags
20
As an Amazon Associate, we earn from qualifying purchases.
Inputs
Result
20 kids × 3 slices × 0.7 = 42 slices. 42/8 = 6 pizzas. Cost: 42 × $1.50 = $63. Cake: ceil(20 × 1.1 × 1.0) = 22 servings → 1/4 sheet. Goody bags: 20 × $5 = $100.
Inputs
Result
30 adults × 8 oz × 1.0 = 240 oz. Cake: ceil(30 × 1.1) = 33 servings → 1/2 sheet. Drinks: 30 × 3 = 90. Balloons: 30 × 2 = 60.
For kids ages 6–12, plan 70% of adult portions. A pizza party needs 3 slices per adult or ~2 slices per kid. For 20 kids, that is 40 slices or 5 large pizzas. Adult parties need full portions: 2 hot dogs/burgers each or 8 oz of finger foods per person.
| Guests | Pizza (slices) | Hot Dogs | Finger Foods (oz) |
|---|---|---|---|
| 10 kids | 21 (3 pizzas) | 14 | 56 oz |
| 20 kids | 42 (6 pizzas) | 28 | 112 oz |
| 15 adults | 45 (6 pizzas) | 30 | 120 oz |
| 30 adults | 90 (12 pizzas) | 60 | 240 oz |
An 8-inch round cake serves 10–12, a 1/4 sheet serves 24, a 1/2 sheet serves 48, and a full sheet serves 96. For 20 guests, a 1/4 sheet cake is sufficient. Plan 1.1 servings per guest to account for seconds. Kids and toddlers eat smaller pieces, so a cake for 20 kids can serve up to 22.
One goody bag per child guest. Budget $3–5 per bag for a mix of small toys, candy, stickers, and a themed item. For 20 kids, that is 20 goody bags at $60–$100 total. Goody bags are standard for ages 1–12 but generally not expected for teen or adult parties.
Plan 2 balloons per guest for general decoration. For 20 guests, that is 40 balloons. Latex balloons cost $0.10–0.25 each unfilled. Add a dozen extra for a balloon arch entrance or photo backdrop. Helium-filled balloons float for about 8 hours (latex) or 3 days (foil).
Read our guide
Read our guide
Read our guide
Plan baby shower supplies
Graduation party planner
Cake size by servings
Explore all our free event planning and utility tools
Last Updated: Jun 18, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.