John Calvin wrote, "Paul makes grace common to all men, not because it in fact extends to all, but because it is offered to all. Although Christ suffered for the sins of the world, and is offered by the goodness of God without distinction to all men, yet not all receive Him" (Comments on Romans 5:18).
No one can say, I'm not saved because God has not offered grace to me. John Calvin made this clear when he stated that grace "it is offered to all." The reason so many are lost is not on God's part, but man's rejection of the grace offered. Unbelief says no to the grace of God in the gospel of Jesus Christ (John 3:36).
Salvation comes as people receive the grace of God in Christ (John 1:12). Condemnation comes to people who do not receive the offer. Unbelief puts the responsibility on those who receive not the grace of God. It is the goodness of God who offers grace to all (John 3:17).
Notice that Calvin clearly declared that "Christ suffered for the sins of the world." Yes, the sacrifice of Christ at the cross is sufficient in value and worth to save each one and all. Yet, it shall save one and all who believe on the Lord Jesus Christ (Acts 16:30-31). However, those who reject the love of God in Christ Jesus will perish (John 3:16). God's grace is sufficient for all; God's grace saves all who believe.