Post-and-rail fencing is a fairly basic installation, but it's not a cheap project. To figure up the overall cost and determine if it's in your budget, you need to decide several things, such as the type of fencing and where it will be located in the yard.
Go to a home-improvement store and look at the types of fencing available. Decide on the style you would like to consider and write down the price of the rails and posts. There are split rail components that slide through slots in the post and other fence rails that screw onto the posts. Also, consider how many rails you prefer in each section -- perhaps two or three -- and if you want wood or vinyl. Gather prices on other items such as a gate, any necessary hardware, cement, gravel and tools. You'll need a posthole digger and drill.
Take a measurement of the fencing rails and write it down.
Measure the length of each line of fence needed and divide this by the measurement of the fence rail. This tells you how many rails you need per row of rails.
Take the number you just determined in step 3 for how many rails you need for one row, and multiply by how many rails you want in each section, as decided in step 1. This will give you the total number of rails you need.
Use the number of rails for one row that you determined in step 3 and add one to it to determine the number of posts you need for the fencing job. Add two if you are going to install a gate.
Multiply the total number of rails from step 4 by the price per rail, and multiply the number of posts in step 5 by the cost per post. To determine the total cost, add the total prices for rails and for posts together, plus the prices of other required supplies such as cement, gravel, hardware and a gate.