As you increase your frame and weapon slots with more and more items, the question always arises . . . with only 60 mods points (using Orokin reactors and cells) what can I put on my frame, weapon or sentinel to really make me a bad ass, and how many forma will it take? This is the site for you . . .
By choosing the category, such as Warframe or Primary Weapon, for example, then choosing the particular item in question, you will view a screen where you can add and subtract mods, increase or decrease their strength and determine how many forma it will take. Afterwards, you will have a visual representation of your final build.
If only the RNG Gods were as nice to you.