Although Jesus is usually pictured carrying the whole cross, this may not have been the case. The practice was to have a permanent stake on the ground with the victim to be crucified having to carry the crossbar on his back to the stake. Did they make an exception for Jesus and force Him to carry the whole cross? We don’t know.
Solid wood
In John 19:17, John says Jesus carried the cross while in Matthew 27:32, Mark 15:21 and Luke 23:26 we are informed that Simon of Cyrene helped Jesus to carry the cross. There are no exact figures on the weight of the cross. It is believed to have been made of solid wood , so the whole cross is estimated to be over 300 pounds (136 kilograms) while the crossbar is estimated to be around 70 -90 pounds (32-41 kilograms) .
Weakened by the torture, scourging, humiliation and beatings, carrying even a crossbar would have been too much for Jesus. That is why they had to force Simon to help Jesus bear the burden. But there was one burden Simon could not help Jesus with – the burden of the sin of all mankind; past, present and future.
Burden of sin
Only Jesus could remove this burden of sin from us because He is God in the flesh (John 1:1, Colossians 2:9). If He had not done this, we would be separated from God forever (Romans 6:23). Our God is holy and righteous, but we are not because we have broken His perfect laws. We deserve to be punished. But because God is also love, He wants us to be reconciled with Him. The only way out was for Jesus, who is perfect in every way, to become a perfect sacrifice and take upon Himself the sin of mankind. He took the punishment we deserve and thus satisfied the requirement of the law that sin be punished (2 Corinthians 5:21, 1 Peter 2:24).
For the sinless Jesus, much worse than the physical weight of the cross was the weight of the sin of mankind. Praise God that with Jesus’ death and resurrection we are not weighed down by our sin anymore.