Your calculations are wrong. They assume 1 tsp borax = 1 gram borax. This is wrong. 1/4 tsp borax = 1 gram = 1,000 miligrams. Therefore, 1/8 tsp = 500 mg borax. 500 * .113 = 56.5 boron. So, 1/8 tsp borax provides 56.5 mg of boron. These are the rough measurements provided in the Walter Last article that started the whole borax thing and seems to be based on serious analysis. I'll go by them. Thanks,