Would like a formula for what to charge a tenant for wear and tear on carpet.

I don't think you CAN charge the tenant for that. That's part of the cost of doing business as a landlord. Unless, the tenant did some specific damage, like a big hole or a stain you can prove with pictures wasn't there before they moved in, it's your cost. Carpets are expected to wear out over time. Wear and tear is not considered damage, at least not in California, where I live.
Asking (landlord)

If it can be cleaned charge him the cost of having it cleaned, If it needs to be replaced charge a percentage of cost depending on how long he lived there or how long the carpet was in place, if he lived there a long time mabe you'll have to write it off as normal wear and tear. Just an idea?

Right. If you can prove the carpet was clean when the tenant moved in, you can charge for cleaning (or ask the tenant to clean it).

I guess asking the tenant to take care of it would be fare, and probably the most civil way also, if that doesn't work you could suggest that it will be taken out of renters damage dep. At time of move.

There is none since nromal wear and tear is not chargable. That is just part of standard rent and cost of renting.

If the carpet was damaged, holes, stains that can not be cleaned out, then that can be held against the deposit.

I take it that this is a serious question, so here is the formula

Take the depreciated value of the carpet at the date of tenancy and subtract the depreciated value at end of the tenancy and divide that amount by the number of months that the tenant has lived there and now take this number and divide it into the cost of replacement carpet and then multiply that amount by 0.

This formula will give you exactly what the landlord is entitled to.

Every business including the landlord business has its inherent costs. The cost of maintaining the rental premises is deducted from the rent leaving the gross profit margin. Part of those expenses is to watch just as you would watch your own carpet in your own home depreciate with use over a period. Tenants are usually responsible for the ordinary cleanliness of the rental premises as determined using the reasonable person theory. One of the costs of maintaining a rental premises is insurance. Use it when the need arises.

The best tenant is one who will treat the rental premises as if he owned it or as he would want his place treated if her were a landlord. If a tenant is treated with respect and has respect for him or herself, they will respect the rental premises. If they are not treated fairly and with respect, the landlord is often treated accordingly.

If a new carpet is installed prior to the tenancy and the landlord knows that a family of five is going to live there and intend to stay for a substantial period, that landlord has best be prepared to replace the carpet when they move out at his expense and factor this cost into the rental charge on the unit.

I still think this question is a joke.