Mud Weight & Hydrostatics
Drilling-fluid pressure maths — hydrostatic pressure, pressure gradient, equivalent mud weight (EMW), equivalent circulating density (ECD) and barite weight-up. Field and metric units, fully offline.
Open Mud Weight & Hydrostatics →What is the mud weight & hydrostatics calculator?
A drilling-fluid pressure calculator that runs entirely in your browser. It works out the hydrostatic pressure of a mud column, converts between mud weight and pressure gradient, finds the equivalent mud weight (EMW) that a given pressure represents, adds annular friction to give the equivalent circulating density (ECD), and tells you how much barite is needed to weight the mud up to a target density. Field units (ppg, ft, psi) and metric units (SG, m, bar) are both supported, and every result updates as you type. Nothing is uploaded — the maths uses the standard Lapeyrouse/IADC constants and stays on your device.
How to use Mud Weight & Hydrostatics
- Choose your units — Use the Field / Metric switch at the top. Field is ppg, feet and psi; metric is specific gravity (SG), metres and bar.
- Pick a calculation — Select a tab — Hydrostatic, Gradient, EMW, ECD or Weight-up — for the value you need.
- Enter the known values — Type the mud weight and true vertical depth (or pressure, annular loss, or current and target weights). Results appear immediately.
- Read the result — The main figure is your answer; the smaller line shows a helpful equivalent, such as the gradient or the increase over static density.
Frequently asked questions
Which depth should I use — measured or true vertical?
Always true vertical depth (TVD) for pressure. Hydrostatic pressure depends on vertical height, not on how far the bit has travelled along a deviated hole.
What constant does it use?
Hydrostatic pressure uses 0.052 in field units (psi = 0.052 × ppg × ft) and 0.0981 in metric (bar = 0.0981 × SG × m). These are the standard drilling constants.
How is the barite figure worked out?
It uses a mass balance with API barite at SG 4.2 (35 ppg). The field result is 100-lb sacks per barrel of the original mud; the metric result is kilograms per cubic metre. Adding barite increases the total mud volume, which the tool also reports.
Does it work offline?
Yes. There are no dependencies and no network calls, so it runs on a rig laptop with no signal, and your last inputs are saved on your device.
Tips
- ECD uses the annular pressure loss above the point of interest — read it from your hydraulics model or standpipe data at the flow rate you are circulating.
- The gradient tab works both ways: enter a mud weight to get its gradient, or enter a gradient to get the equivalent mud weight.
- Target mud weight must be below barite density (35 ppg / 4.2 SG) and above the current weight, or the weight-up result cannot be computed.