Whether you lose any over the course of bringing them to laying age will also depend in part on the conditions you provide for them at your home. For instance, if your brooder isn't hot enough---or if it's too hot!---you may lose some chicks. Baby chicks can drown in waterers that are too deep, and if waterers or feeders are not securely seated, they can even knock over a waterer or feeder onto themselves and get hurt that way. If you have lots of predators around, or a coop that's not secure, or if you have a dog that has access to your birds, you may lose some as they grow to adulthood. Of course, there isn't a way for us to evaluate the risk there may be in your particular circumstances. If you're prepared with secure surroundings and good brooder conditions, though, you shouldn't have problems. If you absolutely cannot have fewer than, say, five hens, though, you may want to consider ordering extras--IF you have a means to keep or responsibily rehome any extras you don't want to keep permanently.
Another thing to consider is that losses can happen during shipping. Losses during shipping are rare, but they do happen. Again, if you absolutely must have five no matter what, AND you have the means to keep or responsibly rehome any extras without difficulty, it would be reasonable to order more than you need. For example, if you are ordering one silkie as a special pet for your 6 year old, and that one special chick drowns in its waterer, it could be devastating! Please take this into consideration when you are constructing your chick order, whether you are ordering from us or from another hatchery. If you cannot do without a certain chick, AND if you have the means to rehome extra chicks easily, then you may want to order extras of any special breed you want, whether it's a funky breed for a child, or a special chocolate egg layer for you. Remember, especially with small orders, any loss can be a big deal. If you lose two in an order of 25 or 50, it's quite different than if you lose two in an order of only five, as you can imagine!
The last thing to consider when determining whether to order extras is that sexing day old baby chicks is an art, not a science, so sexing errors do happen. While we have a 100% sexing accuracy guarantee (other hatcheries guarantee only 90%), that doesn't mean there will be no errors. The 100% guarantee simply means that we cover all errors (other hatcheries cover 90% of their errors); it doesn't mean that errors never happen.
Golden Campine rooster
So again, if you have a small order and you absolutely MUST have a certain number of hens---if you're unwilling to take the smallest risk of having fewer, and you have a plan if you end up with a larger flock---then you'll probably want to order extras, just in case. While any errors and losses are covered by our guarantees and refunded according to our policies, remember that if you do experience those problems, we cannot ship just one or two birds at a time to make up for the loss or error. In most cases you'll simply be eligible for a refund; read our policies for details.
Lastly, if you do decide to order extras, we recommend you order at least two, because it's so much easier for any potential adopter to introduce two birds to another flock than just one. If just one is introduced to a new flock, that one will be singled out as an invader. However, if there are companions that can all be rehomed together, introducing them to a new flock is easier, since they'll have each other. That way, any aggression from the new flock will be spread out a little. You're more likely to find adopters if you have two or more extras, because it will be so much easier on the person adopting to introduce a few rather than just one.