You need a specific formula for this (attached).
Principal = Annual Payout * [(1 + r )^n -1] / r * (1 +r)^n
Principal = 45,000 * [(1.031)^25 -1] / .031*(1.031)^25
Principal = 45,000 *
(<span>
<span>
<span>
2.1451942889
</span>
</span>
</span>
-1) /
<span>
<span>
<span>
0.066501023
</span>
</span>
</span>
Principal = 45,000 *
(1.1451942889) /
<span>
<span>
0.066501023
</span>
</span>Principal = <span><span><span>51,533.7430005
</span>
</span>
</span>
/
<span>
<span>
0.066501023
</span></span><span><span><span>Principal = 774,931.582638962
</span>
</span>
</span>
Principal = 774,931.58
Source:
http://www.1728.org/annupay2.htm
look at second formula