120pc是多少ly？
120pc = 391.3877ly
是391.3877ly，所以說成391ly也沒問題——四捨五入的誤差在0.5%以內。
反過來，120ly是多少pc？
120ly = 36.7922pc
計算公式: ly = pc × 3.261564
該數值前後的 pc → ly
30 pc97.8469ly
40 pc130.4626ly
50 pc163.0782ly
60 pc195.6938ly
70 pc228.3095ly
80 pc260.9251ly
90 pc293.5407ly
100 pc326.1564ly
110 pc358.772ly
120 pc391.3877ly
130 pc424.0033ly
140 pc456.6189ly
150 pc489.2346ly
160 pc521.8502ly
170 pc554.4658ly
180 pc587.0815ly
190 pc619.6971ly
200 pc652.3128ly
210 pc684.9284ly
220 pc717.544ly