The entrants never divide into the runners
The Grand National has a field of 34. Your office has 17 people, so that is two each with nothing spare. Add one more person and it is 34 into 18: one each, with sixteen left over, and now there is a decision to make.
What happens to those leftovers is the only thing anybody ever argues about in a sweepstake, and it is the part every free generator glosses over. There are three honest answers.
Spread them
Some people get an extra one. Fair in expectation, and it looks unfair on the night, because somebody holding three is visibly better off than somebody holding two. Draw the extras openly in front of everybody and the appearance problem disappears.
Put them in the kitty
The spare runners belong to the pot rather than to a person. If one of them wins, the money goes to whatever the kitty is for. Clean, and it has to be said before the draw, or it looks exactly like the organiser keeping the difference.
Leave them out
Simplest, and it quietly changes the odds. Leave 6 of 40 out and there is a 15% chance that nobody in the room holds the winner at all. Worth announcing, because the first time it happens everybody assumes something went wrong.
The fourth option, where the organiser quietly keeps the spares, is the one this tool will not do. The result says which of the three you chose, so nobody has to take anyone at their word afterwards.
No odds, no form, no betting links
This draws names out of a hat and prints the result. It does not tell you which horse is favourite, it carries no prices, and it does not link anywhere you could back one.
That is deliberate and it will not change. A workplace sweepstake is a raffle that happens to have horses in it: everybody pays the same, everybody gets a random entry, the pot is shared out. The moment a tool starts publishing form it has become something else, aimed at a different person, with a different set of obligations attached to it.
Pay out everything you take in
In the UK, a workplace sweepstake where the whole pot goes out as prizes, run for the people taking part rather than for profit, is normally an exempt work lottery. Nothing to register and nothing to pay.
Keeping a slice of the pot, or selling entries beyond the workplace, moves it into different territory. For anything bigger than an office, the licensing team at the council deals with this all the time and it is a phone call rather than a problem.
A draw you can reproduce
Both sides are shuffled, runners and people, so the order somebody typed the names in decides nothing at all. If only one side were shuffled, whoever was typed first would quietly get the first horse out every time.
And the same settings always produce the same draw, which means you can run it again in front of anybody who thinks it was rigged. Everything happens on your own machine, and nothing is uploaded.
Common questions
What do I do with the runners left over?
There are three honest answers and the tool asks which one you want. Spread them, so some people get an extra. Put them in the kitty, so a win goes to the pot. Or leave them out, which is simplest and quietly means nobody may hold the winner at all. What you must not do is let the organiser take them.
Which is fairest?
Spreading is fairest in expectation, and it looks uneven on the night because somebody with three is visibly better off than somebody with two. Drawing the extras in front of everybody fixes the appearance. The kitty is cleanest, as long as it is announced before the draw rather than after it.
What happens if I leave the spares out?
With 6 of 40 runners not drawn, there is a 15% chance nobody in the room holds the winner. That is worth saying out loud beforehand, because the first time it happens somebody will assume a mistake was made.
Why are there no odds or favourites?
Because a workplace sweepstake is a raffle with horses on it, and it stops being that the moment form gets involved. This draws names out of a hat and prints the result. It does not say which one is favourite, it does not link anywhere you could place a bet, and it never will.
Is an office sweepstake legal?
In the UK, a workplace sweepstake where the whole pot is paid out as prizes, run for the people taking part rather than for profit, is normally an exempt work lottery. Keeping a cut, or selling entries outside the workplace, is a different thing. The licensing team at your council is the right place to ask if you are unsure.
Can I use my own list of runners?
Yes. Paste them one per line and they are used instead of the numbered field. Leave it blank and you get numbered entries, which is enough when the racecard is not out yet.
Can I prove the draw was not fixed?
The same settings always produce the same draw, so you can run it again in front of anybody who asks. Both the runners and the people are shuffled, so the order somebody typed the names in decides nothing.
How do the prizes work?
You set the percentages. The tool checks they add up to 100 and says so if they do not, because a split leaving 10% unaccounted for tends to get noticed after the race rather than before it.