Is there a good free substitute for BP's investment calculators

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I really don't understand why I am stuck to using the calculators only 5 times per account. I know that it is an incentive to buy the Pro plan, but I am not in the position to spend for the pro plan. Especially when I am brand new to REI and I am no where near ready to make a deal. But I need to practice crunching numbers and seeing the big picture so I can find good deals

Are there other free substitutes  to BP's calculators? And I mean free, not "you tried it free for 3 seconds, now here is a pay wall"