This is a potentially tricky question, because while 18th century thinkers were inspired by the Magna Carta, their notions of what was actually spelled out by that document were sometimes a bit off the mark.
For instance, because the Magna Carta stipulated that the Crown couldn't impose taxes without the "general consent of the realm," people in the American colonies believed that it set the precedent for "no taxation without representation."
But as Claire Breav and Julian Harrison point out in their article for the British Library (see link below), this "general consent of the realm" referred to the consent of "leading barons and churchmen," not the citizenry at large.
Still, these words certainly contributed to the theory that governments shouldn't tax without consent. Likewise, other parts of the Magna Carta -- particularly Chapters 39 and 40 -- helped shape the thinking of the people who created the United States Constitution and Bill of Rights. Here are three key concepts found in the Magna Carta that influenced the founding fathers.
1. Due process or rule of law
Chapter 39 of the Magna Carta says:
"No free man shall be seized or imprisoned, or stripped of his rights or possessions, or outlawed or exiled, or deprived of his standing in any other way…except…by the law of the land."
This wording is echoed in the Fifth Amendment, where it says:
"No person shall…be deprived of life, liberty, or property, without due process of law."
2. Trial by a jury of peers
Chapter 39 of the Magna Carta also mentions trial by jury -- the "lawful judgment of (an accused man's) equals." Eighteenth century thinkers believed this was a crucial liberty; one of the complaints in the Declaration of Independence is that King George has often deprived Americans of it. The right to a jury trial is included in the Constitution and the Seventh Amendment.
3. The right to a speedy trial
Chapter 40 of the Magna Carta says:
"To no one will we sell, to no one deny or delay right or justice."
This concept was incorporated into the Sixth Amendment which guarantees "...the right to a public trial without unnecessary delay…"