Knowing how to build a baseball diamond starts with staking a 90-foot square at home plate, then proving it true with a diagonal measurement instead of a tape-measure guess. A standard infield’s diagonal, home plate to second base, measures 127 ft 3 3/8 in (38.80 m); Little League’s smaller square measures 84 ft 10 in (25.86 m). If a staked corner doesn’t land on one of those two numbers, the diamond isn’t square yet.
Field diagram
Start from the official dimensions, not a guess
Every figure below comes from the Official Baseball Rules, already sourced on this site’s baseball field dimensions guide, part of the baseball hub. The diagonal rows are official MLB figures too, not a Pythagorean estimate: Rule 2.01 states them directly, and they run less than a millimeter from the true geometric value of a 90-foot square.
| Measurement | Figure | Applies to | Status |
|---|---|---|---|
| Base distance (home plate to first base, along the foul line) | 90 ft (27.43 m) | MLB, NFHS | Official rule |
| Base distance, Little League Major Division | 60 ft (18.29 m) | Little League Major (and below) | Official rule |
| Home plate to second base (the diagonal) | 127 ft 3 3/8 in (38.80 m) | MLB, NFHS | Official rule |
| Home plate to second base, Little League Major Division | 84 ft 10 in (25.86 m) | Little League Major (and below) | Official rule |
| Pitching distance (front edge of the rubber to the back point of home plate) | 60 ft 6 in (18.44 m) | MLB, NFHS | Official rule |
| Pitching distance, Little League Major Division | 46 ft (14.02 m) | Little League Major (and below) | Official rule |
Set the four corners before marking any lines
A square is easiest to stake from its corners, not by chasing one baseline at a time. Start at the back point of home plate and run two string lines toward first base and third base, holding them at a right angle to each other (checked with the 3-4-5 method below). Measure 90 ft (27.43 m) along each string to mark first base and third base, or 60 ft (18.29 m) for a Little League Major infield. From each of those two points, swing a tape the same distance toward the other side of the square; the point where both tapes meet is second base.
Only after all four points are fixed should the baselines themselves be strung and chalked. Marking the corners first, then connecting them, keeps a small error in one measurement from compounding into every line that follows, the same order of operations used for staking out a rectangular court.
Check the square with both diagonals
A true square has two equal diagonals, and the baseball infield is a true 90-foot square, so this check works without any extra geometry. Measure from home plate to second base, then separately from first base to third base. Both should read 127 ft 3 3/8 in (38.80 m) on a standard infield, or 84 ft 10 in (25.86 m) on a Little League Major infield. If the two diagonals don’t match each other, the corners aren’t square yet, even when every side already measures exactly 90 ft (or 60 ft). A parallelogram can have four correct side lengths and still be crooked; only matching diagonals confirm the right angles.
The 3-4-5 check for the right angle at home plate
Before stretching either baseline out to its full 90 ft, confirm the angle at home plate is a true right angle with a 3-4-5 triangle: measure 3 ft along the line toward first base and 4 ft along the line toward third base, then measure the distance between those two points. On a true right angle, that third side is exactly 5 ft. Doubling those numbers to 6, 8 and 10 ft gives a longer baseline and a more precise check once the lines are staked further out. This is a general property of right triangles, not a baseball-specific rule, and it catches a crooked angle before a single tape is run the full 90 ft (the same check, scaled down, is used in this site’s guide to laying out a tennis court).
Setting the pitcher’s plate
The pitcher’s plate sits on the line running from the back point of home plate through second base, not off to one side. Measure 60 ft 6 in (18.44 m) from that point to the front edge of the rubber for a standard infield, or 46 ft (14.02 m) for a Little League Major infield. Because that line is the same one used for the home-to-second diagonal check, confirming the diagonal first also confirms the pitcher’s plate sits on the correct line before its distance is measured out.
Checking the mound and the bases once they’re set
None of the figures above fix the height of the mound or the size of the bases, so they’re worth a separate check once the diamond’s corners are staked. MLB’s bases are 18 in (0.46 m) square, a size Rule 2.03 moved up to from 15 in for the 2023 season; Little League Rule 1.06 still allows a bag of 14 to 15 in square. The professional mound stands 10 in (0.25 m) above the level of home plate; Little League’s Major Division mound stands 6 in (0.15 m) above it. Getting the square right first makes these last two checks straightforward, since the mound and the bases both sit on lines already fixed by the staking above.
Overhead plan
The same surface seen from straight above, drawn to scale. Nothing is foreshortened here, so every figure can be read off the drawing the way a tape measure would take it.
Detail sheet
A rule book fixes more than the shape of the surface, and the rest of it is too small to draw at court scale: a mark a few centimeters long, a post standing a meter off the sideline, the clearance around the whole thing. Each one here has its own frame and its own scale.
Frequently asked questions
How do I find second base when staking a baseball diamond?
Measure 90 ft (27.43 m) from first base and separately 90 ft from third base; the point where those two measurements meet is second base. For a Little League Major infield, use 60 ft (18.29 m) from each base instead.
What is the exact diagonal of a 90-foot baseball infield?
127 ft 3 3/8 in (38.80 m), measured from the back point of home plate to the center of second base. That figure comes directly from the Official Baseball Rules, Rule 2.01, not from a separate calculation.
Is a Little League diamond just a smaller version of the same shape?
Yes. Little League’s Major Division uses a 60 ft (18.29 m) square with an 84 ft 10 in (25.86 m) diagonal and a 46 ft (14.02 m) pitching distance: the same square shape, staked at a smaller scale.
Do both diagonals of the infield have to match exactly?
Yes. A square’s two diagonals are always equal, so measuring both home-to-second and first-to-third is the fastest way to catch a corner that drifted out of square, even if every side still measures the right length on its own.
Where is the pitcher’s mound measured from?
The pitching distance is measured from the front edge of the pitcher’s plate to the back point of home plate, along the home-to-second line: 60 ft 6 in (18.44 m) for a standard infield, 46 ft (14.02 m) for Little League’s Major Division.
Official sources
- Major League Baseball / Office of the Commissioner of Baseball, Official Baseball Rules, 2025 Edition, Rule 2.01, as already cited on this site’s baseball field dimensions guide.
- Little League Baseball, Rules Instruction Manual, Playing Rules 1.04 to 1.08, 2018 edition, as already cited on this site’s baseball field dimensions guide.
Figures checked against those documents on 15 October 2026, matching the verification already recorded for this site’s baseball field dimensions guide. The methodology page explains how each figure is labeled as a rule or a derived calculation; report an error through corrections.
Photo: Tyler Lahti via Wikimedia Commons (CC BY 2.0).