About DrillingIt

DrillingIt is a small, independent, advertising-supported site about the drilling world — rigs and wells, mud hydraulics, casing and cementing, drilling performance, and oil, gas, and geothermal extraction — built around six field calculators, a Drilling Museum, and a library of explainers.

How the Calculators Are Built

Every tool here runs one named, published oilfield formula — there is no hidden model and no proprietary dataset behind any of them. The Hydrostatic Pressure Calculator uses the standard field equation HP = 0.052 × mud weight (in ppg) × true vertical depth (in ft). The constant 0.052 is simply the unit conversion that turns a mud-weight column into psi per foot of depth, and it is the same constant taught in well-control courses and printed on rig-floor reference cards.

The Annular Velocity Calculator works out the up-hole speed of drilling fluid in ft/min from pump flow rate in gpm and the hole and pipe diameters in inches, using the standard relationship that divides 24.51 times the flow rate by the difference between the hole diameter and the pipe diameter, each squared. The Rate of Penetration (ROP) Calculator does simpler division — footage drilled over rotating hours — to get the ft/hr figure crews use to benchmark a bit run.

The Drilling Cost Per Foot Calculator follows the classic bit-economics equation: bit cost plus rig day rate applied to rotating and trip hours, divided by footage drilled, giving a dollars-per-foot figure that lets two very different bit runs be compared on equal footing. The Hole Volume Calculatorconverts a diameter in inches and a length in feet into barrels using 1029.4, the standard oilfield capacity factor for a cylindrical volume — the same constant used for open-hole, casing, and pipe-capacity work on mud, displacement, and cement-and-spacer jobs. The Equivalent Circulating Density (ECD) Calculator adds the annular pressure loss, converted through true vertical depth with the same 0.052 constant, back onto mud weight to show the effective density the formation feels while circulating.

None of these formulas were invented for this site. They are the everyday equations of drilling engineering, and every tool simply does the arithmetic on the numbers you enter and rounds the result. If a formula, a unit, or a constant looks wrong to you, we want to know — see below.

What This Site Is (and Isn’t)

DrillingIt is independent and not affiliated with, endorsed by, or speaking for any rig contractor, operator, service company, or standards body — API, IADC, or otherwise. It runs on advertising, which is how it stays free with no account required. The calculators are built for planning and learning: they return estimates from the numbers you supply, not certified engineering output. They are general informational content, not professional engineering, safety, or regulatory advice, and any real well plan, hydraulics program, or casing design should be checked against qualified personnel, current equipment specifications, and the applicable standards for your operation before anyone acts on it.

Questions about how a calculator works, a formula that looks off, or a tool you think is missing — get in touch.