Directional drilling pitch & depth calculator

Pitch is the up-or-down angle of the drill head, read off the locator. It is usually shown as a percent grade: the rise or fall divided by the horizontal distance, times 100. A pitch of -20% means the head is dropping 20 feet of depth for every 100 feet it travels forward.

Multiply the rod length by the pitch percent. A 10 foot rod at 20% pitch drops about 2 feet (10 × 0.20). A 15 foot rod at the same pitch drops about 3 feet. That is the field-standard way to plan a bore, one rod at a time.

Take the arctangent of the pitch divided by 100. So 20% is about 11.3 degrees, 50% is about 26.6 degrees, and 100% grade is exactly 45 degrees. Most HDD electronics stop reading reliably past about 45 degrees.

Divide your target depth by the drop per rod, and round up. To reach 6 feet deep at 20% pitch with 10 foot rods, each rod drops 2 feet, so it takes 3 rods — and about 30 feet of surface run to get there. After that you flatten the pitch toward 0% to run level at depth.

Depth of cover depends on what you cross and who governs it. Under a road the common target is 36 to 48 inches; utility and DOT permits often spell out an exact minimum, and railroad or highway crossings go deeper. The number the inspector cares about is the shallowest point of the bore, so plan and record that, not the average.

Two limits. The tooling: drill rod bends only so far, commonly about 10% of pitch change per rod, so you cannot dive or climb instantly. The electronics: most locating gear reads to about 45 degrees (100% grade). Steep entries are done in small pitch steps, a rod at a time.