PA1B has made a nice calculator to design RF attenuators from standard resistors. You can select if you want to use 0,25W, 1W, 3W, 5W resistors, how much power in W the attenuator shall handle and the attenuation in dB. https://pa1b-qrp.blogspot.com/p/power-attenuator-calculator.html
Here you can download the Excel file (it is safe to use):