A great all-in-one freeware takeoff and landing performance calculator by the name of Airplane Toolbox by Apsoft can be found at X-Plane.Org. It works just fine as a stand-alone utility making it useful for all flight simulator platforms.
Once you find the executable contained within the “BIN” folder, you will need to perform a couple of tasks before you can get going.
Firstly, it needs some navdata which can be obtained from Navigraph or Aerosoft Navdata Pro.
Look in the instructions for details of what is needed, so if you have a navdata subscription then you’ll likely be able to use data that you already have installed, or at the very least download the needed data as a manual install. If not, then it is quite possible that some payware already within your installation may already have the necessary navdata available.
Next, you will have to build an airport runway database, hence the reason that the toolbox requires navdata. The download page here also has links to two zip files holding a number of pre-formulated generic and/or dedicated profiles for the most popular aircraft types which can also be edited for fine tuning, otherwise you are free to create your own profiles, but sadly no 777 to keep T7 fans happy.
After that, you are good to go; simply enter your departure ICAO, select the departure runway, hit the WX button for the toolbox to download the METAR, then enter you takeoff weight and one or two other details such as anti-ice and runway surface, and you’ll be rewarded with v-speeds and assumed temperatures. Much the same routine can be done for landing performance data too.