Ton-Mile Calculator
Calculate round trip ton-miles for drilling line fatigue management. Track cumulative service and get cut/slip recommendations.
Round Trip Ton-Miles
Buoyed drillstring weight
Per API / manufacturer spec
Trt = (D / 5280) × (2Wm + 2Wb + Ws × D / (2 × 5280))
Simplified: accounts for average string weight during trip (linearly varying hookload).
Round Trip Ton-Miles
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Stands Pulled
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Avg Hookload
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tons
Trips to Cut Limit
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Cumulative Ton-Mile Tracker
Log round trips to track cumulative ton-miles. Data saved in your browser.
| # | Depth (ft) | Type | Ton-Miles | Cumulative | Note |
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Cumulative Ton-Miles Over Trips
How this was calculated
Round Trip Ton-Miles (simplified): Trt = (D/5280) × [2×Wb + 2×Wm × D/(2×D) + Wdp×D/(2×5280)]
More precisely: T = (D/5280) × [Wb + 0.5×Wm] × 2 for a round trip, where Wm is string weight in mud and Wb is traveling block weight. The factor of 2 accounts for trip out + trip in.
Cut/Slip Recommendation: When cumulative ton-miles approach the manufacturer's limit (typically 400-800 ton-miles for common drilling lines), the line should be cut and slipped to move fatigued wire away from sheave contact points.
Assumptions: Hookload varies linearly from block weight (empty hole) to full string weight. Friction, deviation, and line efficiency not included in this simplified model.
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Book a free strategy call →Understanding Ton-Miles and Drilling Line Fatigue
Drilling line (wire rope) is one of the most critical and heavily loaded components in a drilling rig's hoisting system. Every time the drillstring is tripped in or out of the hole, the drilling line experiences cyclic loading as it passes over the crown block sheaves and through the drawworks. This repeated bending under load causes fatigue, which accumulates over time and eventually leads to wire failure if not managed.
Ton-miles is the standard metric for quantifying the cumulative work performed by the drilling line. One ton-mile represents moving a one-ton load a distance of one mile. The total ton-miles for a round trip depend on the depth of the trip, the weight of the drillstring in mud, and the weight of the traveling block and hook. As the string is pulled out, the hookload decreases as each stand is set back, so the average load is approximately half the full string weight plus the block weight.
Manufacturers specify a maximum ton-mile service life for their wire rope (typically 400-800 ton-miles depending on rope grade and diameter). When cumulative ton-miles approach this limit, the line must be cut and slipped (moved through the system) to distribute fatigue across fresh sections of rope. Proper ton-mile tracking prevents catastrophic line failures that could drop the drillstring or injure rig personnel.
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