Benefits of having a Mass said for someone

Can anyone tell me the major benefits of having a Mass said for someone? Does all the grace distributed go to that individual/intention?
Is the amount of grace given contingent on the disposition of those attending and that of the priest’s? Does the Church provide information on this somewhere? Thanks!

Benefits: We are offering the most perfect prayer for that person, the prayer most pleasing to God. Nothing else we could do for that person, no other prayer, even comes close.

“All the grace”: The Mass is the perfect sacrifice of Jesus at Calvary. The grace is infinite. Plenty to go around. Even if the Mass is offered for a specific intention, the Mass is really offered for the whole Church, everyone in the world, all the living and deceased. Just read Eucharistic Prayer 1:

"We come to your, Father, with praise and thanksgiving, through Jesus Christ your Son. Through him we ask you to accept and bless these gifts we offer you in sacrifice. We offer them for your holy catholic Church, watch over it, Lord, and guide it; grant it peace and unity throughout the world. We offer them for {Benedict} our Pope, for {name of Bishop in your diocese} our bishop, and for all who hold and teach the catholic faith that comes to us from the apostles.

"Remember, Lord, your people, especially those for whom we now pray, {names}. Remember **all of us gathered here **before you. You know how firmly we believe in you and dedicate ourselves to you. We offer you this sacrifice of praise for ourselves and those who are dear to us. We pray to you, our living and true God, for our well-being and redemption …

“Remember, Lord, **those who have died **and have gone before us marked with the sign of faith, especially those for whom we now pray, {names deceased loved ones whom the celebrant or parishioner wishes to offer before God}. May these, and all who sleep in Christ, find in your presence light, happiness, and peace …”

And even though the priest is offering the Mass for the specified intention, each person attending Mass can (and should) be offering it for their own intention (the same one or a different one).

Amount of grace: We just have to leave that up to God. He answers prayer in whatever way He sees fit. Trust that He knows best how to distribute graces.

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