A kilogram equals about 2.2 pounds.
A kilogram equals to 2.2 pounds. We don't use "to" after the verb "equal".
A kilogram amounts to 2.2 pounds. -- but unusual
A kilogram is equal to 2.2 pounds.
A kilogram is equivalent to 2.2 pounds.
They mean more or less the same, but "about" in the first sentence indicates clearly that the conversion is only approximately -- that is, one kilo is not exactly 2.2 pounds.
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