Miami University bands its international merit money by grade average, so you can work out roughly where you land before you apply. A US-equivalent 3.25 or an IB score of 36 puts you in line for up to half of tuition, and the bands step down to 20% at a 2.50 average.
Every new international first-year applicant at 2.50 or above is considered automatically, with no separate form and no test scores required. The figures published are for autumn 2027 entry.
Two things are worth planning around. Scholarships are awarded at the time of admission, and priority goes to applications submitted by 1 December, so a late application weakens your position. The award is a share of tuition, which leaves housing, food and fees for you to fund, and renewal each year needs full-time study on the Oxford campus and a 3.0 cumulative average.