The size of the tent needed for 100 guests will depend on several factors, including the type of event, the seating arrangement, and the space required for additional items like a dance floor, buffet tables, and a stage. As a general guideline, you can use the following estimates for common tent sizes:

1 Cocktail Party or Standing Reception: If you're hosting a cocktail party or a standing reception, where guests won't be seated at tables, you'll need about 6-10 square feet of space per guest. For 100 guests, a tent with an area of 600-1,000 square feet would be suitable.

2 Seated Dinner - Round Tables: If you plan to have a seated dinner with round tables, each seating 8-10 people, you'll need about 10-12 square feet per guest. For 100 guests at round tables, a tent with an area of 1,000-1,200 square feet should suffice.

3 Seated Dinner - Banquet Tables: If you prefer long banquet tables, which typically seat 8-12 people, you'll still need approximately 10-12 square feet per guest. So, a 100-guest seated dinner with banquet tables would also require a tent with an area of 1,000-1,200 square feet.

4 Additional Space: Keep in mind that you may need additional space for features like a dance floor, buffet tables, a bar area, and a stage if you're hosting performances or speeches. These can add significant square footage to your tent requirements.

5 Climate Considerations: If your event is in a warm climate, consider providing extra space for shade and ventilation. In cooler or wetter conditions, you may want to include sidewalls and heating to keep guests comfortable.

6 Regulations and Codes: Be sure to check local regulations and safety codes that may affect the size and setup of your tent. You may need to allow for clear pathways and emergency exits.

It's a good practice to consult with a professional event rental company that specializes in tent rentals. They can provide guidance based on your specific needs and local conditions, ensuring that you have the right size of tent to comfortably accommodate your 100 guests and any additional elements of your event.