Calculator

Buoyancy & Tubular Weight

Buoyed pipe weight for open-ended pipe, closed-ended pipe, and pipe carrying a different fluid inside than what's in the annulus.

⚓ Pipe & Fluids
Buoyancy Factor (steel, annulus fluid)—
Buoyed Weight — Open-Ended—
Buoyed Weight — Closed-Ended, No Fluid Inside—
Buoyed Weight — Different Fluid In/Out—
Reference only. Use actual pipe OD/ID from the tally book and confirmed fluid weights for a real string-weight calculation, not catalog nominal values.

The Formulas Used

Buoyancy Factor
BF = 1 − (Fluid Weight ÷ 65.5)
Some references use 65.4 for steel density instead of 65.5 — the difference is under a tenth of a percent. This site uses 65.5 everywhere for consistency; see the drilling formulas cheat sheet for the note on why.
Buoyed Weight — Open-Ended Pipe
W = Weight (air) × BF
Buoyed Weight — Closed-Ended, No Fluid Inside
W = Weight (air) − [(OD² × Fluid Weight) ÷ 24.5]
Buoyed Weight — Different Fluid Inside vs. Annulus
W = Weight (air) + [(ID² × Fluid Weight, inside) ÷ 24.5] − [(OD² × Fluid Weight, annulus) ÷ 24.5]
Per the WellSharp / IWCF field-units formula sheet, buoyed weight of tubulars section.

For the simple open-ended case applied to a full drill string's ton-mile figure, see the ton-mile calculator. Neutral point and where to keep drill collars in compression are on the drilling formulas cheat sheet.

Frequently Asked Questions

Why are there three different buoyed-weight numbers instead of one?

Each covers a different downhole condition. Open-ended pipe (drill pipe, tubing run empty and flowing through) just applies the buoyancy factor to the air weight. Closed-ended pipe with nothing inside it — a plugged joint, a run-in tool — displaces its full outside diameter with nothing pushing back from inside, so it floats more and weighs less than the open-ended case. Different fluid inside versus in the annulus (common in completions, where a lighter packer fluid sits inside tubing against heavier annulus fluid) needs both diameters and both fluid weights, since the two fluids are pushing back with different force.

Why do the open-ended and different-fluid answers come out close but not identical?

The open-ended formula uses a theoretical buoyancy factor based on steel's own density (1 − MW/65.5). The closed-ended and different-fluid formulas instead work directly off the pipe's actual OD and ID — real cross-sectional area, not an assumed steel density. They agree closely because they're describing the same physics, but they aren't forced to match exactly, and the geometry-based numbers are the more precise ones when the actual OD/ID are known.

Does this replace the simple buoyancy factor used elsewhere on the site (ton-mile, drilling formulas)?

No — that one (BF = 1 − MW/65.5) is specifically for open-ended drill pipe weight in a single fluid, which is the common drilling case and still the right tool for that job. This page covers the completions-side variants: closed-ended pipe and two different fluids on either side of the pipe wall, situations that come up in workovers and completions more than routine drilling.