universal credit amounts

i hope some one can help me get my head around these figures regarding universal credit.

i know it doesn't come into force until next year but i like to be prepared.


from what i have read here http://www.legislation.gov.uk/ukdsi/.../regulation/22

and http://www.legislation.gov.uk/ukdsi/.../regulation/36


what you have to do is subtract the work allowance from earned income take 65% of this, plus any unearned income and subtract it from the
elements total.

which my figures would be

wages 1375 - 222 = 1153
65% of this = 749.45

unearned (carers) = 258.91

total deductions = 1008.36


elements standard = 489.06
first child = 272.08
second child = 226.67
low disabled = 123.62
rent = 304.00
total = 1415.43

difference = 407.07 + 1375 = 1782.07

but if i use http://policyinpractice.co.uk/univer...it-calculator/ putting in same amounts used, says i will get this.

base = 489
child = 498
tent = 304

total = 1291 + 1375 = 2666

as you can see there is a vast difference between what i worked out and that site did.
i have not added carers, child benefit or dla as these are not changing.

the first makes me worse off by 140 and the second better by 745.

i was under the impression that you wouldn't be worse off when uc comes into force but i much doubt that i could be that much better off.

am i using the figures correctly ?

thanks :)