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Prize odds calculator: how many prizes for a giveaway?

See the chance of winning per play or per entry, how many prizes you need for the win rate you want, and what the prizes cost in total.

Type of campaign

People see right away if they have won, as with a scratch card or a prize wheel. Enter how many plays you expect and the prizes you have.

Prize 1
Prize 2
Prize 3

What win rate do I want?

The formulas

  • Chance per play for a prize = quantity ÷ expected plays. 20 prizes and 10,000 plays give 20 ÷ 10,000 = 0.2%.
  • 1 in N: N = expected plays ÷ quantity, so 0.2% is 1 in 500.
  • Chance of winning a prize per play = all prizes ÷ expected plays.
  • Expected prizes won = plays × chance per play. When the plays match your estimate, that is all the prizes.
  • Prize budget = quantity × value, added up for all prizes. Prize cost per play = budget ÷ plays.
  • Prize draw, each entry = winners ÷ entries.
  • Prize draw, a person with k entries = 1 − (E − k)/E × (E − k − 1)/(E − 1) × …, with one factor for each winner, where E is the number of entries. It is 1 minus the chance that none of the person's entries is drawn.
  • Prizes for a target win rate = plays × win rate, rounded up.

The calculator assumes fixed odds and that every winner in a draw is a different entry. In Scratcher, you set the quantity and the odds of each instant-win prize, and choose when prizes can be won. See prizes and winners.

How to decide how many prizes a giveaway needs

Start with how many people you expect to play, not with the prizes. A newsletter to 20,000 people might bring 4,000 plays. A campaign in stores and on social media might bring many more. Then decide how often people should win.

  1. Estimate the plays. Use the results of earlier campaigns, or your list size and a realistic response rate. Count plays, not people, if people can play more than once.
  2. Choose a win rate. A low win rate makes winning feel special. A high one keeps people happy and coming back. Many instant-win games mix one big prize with many small ones, such as discount codes.
  3. Work out the quantities. Prizes = plays × win rate. 10,000 plays and a 5% win rate need 500 prizes.
  4. Check the budget. Multiply each prize by its value, and look at the cost per play. Prizes that are cheap for you, such as discount codes, let you offer a high win rate without a high cost.

Instant win or prize draw?

In an instant-win game, every play has a chance, and people see right away if they have won. The odds come from the number of prizes and the plays you expect. If more people play than you expect, the prizes run out sooner; if fewer play, some are left over. That is why it helps to spread prizes over the campaign.

In a prize draw, everyone enters and the winners are drawn at the end. Each entry's chance is the number of winners divided by the number of entries, so the odds depend on how many people take part. Extra entries for sharing or buying raise a person's chance. Read more in instant win or prize draw.

Advent calendars and long campaigns

For a calendar or a campaign that runs for weeks, divide the prizes over the days, so there is still something to win at the end. See what a calendar costs in total, prizes included, in how much a digital advent calendar costs.

Set the odds in Scratcher

In Scratcher, you set the quantity and the odds of each instant-win prize, choose when prizes can be won, and add draws, discount codes and barcodes. Read about prizes and winners. Need to draw a winner from a list you already have? Use our free random winner picker.

Questions

Questions about prize odds

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  • In an instant-win game, divide the number of prizes by the expected number of plays: 50 prizes and 5,000 plays give 1%, or 1 in 100. In a prize draw, divide the number of winners by the number of entries.

  • Multiply the expected number of plays by the win rate you want. With 8,000 plays and a 2% win rate, you need 160 prizes. Use the helper in the calculator to round it for you.

  • That on average one play or entry in 200 wins. It is the same as a 0.5% chance. It does not mean that exactly every 200th player wins.

  • Yes. A person with 3 of 5,000 entries in a draw for 10 winners has about a 0.6% chance, against 0.2% with one entry. The calculator works out the exact number.

  • With fixed odds, the prizes run out sooner. If twice as many people play, they are gone halfway through. Spread the prizes over the campaign, so there is still something to win at the end.