Calculator

Ton-Mile Calculator

Round trip, drilling, coring, short trip, and setting-casing ton-miles for tracking drilling line service life against its API RP 9B rating.

🎣 Rig & String
📏 Round Trip at Two Depths
Buoyancy Factor—
Round Trip TM @ Depth A—
Round Trip TM @ Depth B—
Drilling / Connection TM (3× diff.)—
Coring TM (2× diff.)—
Short-Trip TM (straight diff.)—
🛢 Setting Casing (separate one-way calc)
Setting Casing Ton-Miles—
Reference only. Track cumulative ton-miles against your drilling line's actual service-life rating and cut-and-slip programme, not a one-off figure from this page.

The Formulas Used

Buoyancy Factor
BF = (65.5 − MW) ÷ 65.5
Round Trip Ton-Miles
RTTM = [Wp × D × (Ls + D) + 2D × (2×Wb + Wc)] ÷ (5280 × 2000)
Wp = buoyed drill pipe weight/ft · D = depth · Ls = stand length · Wb = block weight · Wc = buoyed collar weight minus equivalent drill pipe weight over the collar length. Per API RP 9B / Lapeyrouse.
Drilling, Coring & Short-Trip Ton-Miles
Drilling = 3 × (RTTM at B − RTTM at A)
Coring = 2 × (RTTM at B − RTTM at A)
Short-Trip = RTTM at B − RTTM at A
Setting Casing Ton-Miles
TM = [Wp × D × (Lj + D) + D × Wb] × 0.5 ÷ (5280 × 2000)
Wp = buoyed casing weight/ft · D = casing depth · Lj = length of one joint · Wb = block weight.

Buoyancy factor here uses the same 65.5 constant as the drilling formulas cheat sheet's buoyancy section — see that page if a figure needs reconciling to more decimal places.

Frequently Asked Questions

What is a ton-mile and why does drilling line wear get measured in it?

One ton-mile is one ton of load moved one mile of travel — it captures both how heavy the load was and how far the line moved it, which together drive fatigue in the wire rope. API RP 9B tracks cumulative ton-miles against a service-life rating so a line gets cut and slipped before it fails, not after.

Why do drilling, coring, and short-trip ton-miles use different multipliers?

Each covers a different amount of round-trip work. Drilling trips (3×) assume a full round trip to change the bit and back. Coring trips (2×) come out of the hole slower and more carefully but do not need the same repeated connections. A short trip (1×, no multiplier) is a partial round trip, so it gets the plain depth-to-depth difference with no adjustment.

Why does buoyancy factor use 65.5, not the exact density of steel?

Steel works out to roughly 65.44 ppg, and 65.5 is the field-rounded constant almost everyone actually uses. The gap is under a tenth of a percent, but it is worth knowing about if a ton-mile figure will not reconcile exactly against a service company's own numbers.

Is setting-casing ton-miles calculated the same way as a round trip?

No — it is a separate, one-way calculation, because running casing to bottom is not a round trip. It still uses the same buoyed-weight logic, just applied to the casing string being run rather than the drill string being tripped.