If the rider on the front is doing X watts, what does each rider behind them need? The tool solves the group's pace from the leader's power, then estimates the watts at every position behind them.
Mid-line riders save the most. The leader gets a small ~3% bonus when anyone's drafting them.
What the rider pulling is producing. Everything else follows from this.
Power on flat ground goes to two things: pushing air out of the way (aero drag) and rolling the tyres (rolling resistance). The first scales with speed cubed, the second with speed. Drafting only reduces the aero part.
The leader's wattage tells us how fast the group is going, we solve the power equation for speed. The rider on the front also gets a small ~3% drag bonus whenever someone is sitting on their wheel (the trailing rider's low-pressure bubble pushes them along). Then for each follower we apply a position-dependent drag reduction and recompute their watts at that same speed.
Estimates assume a flat road, steady speed, no crosswind, and a representative 80 kg rider with road CdA ≈ 0.32 and Crr ≈ 0.005. Real groups vary, heavier riders, fatter tyres, gusty wind, or a wide gap to the wheel in front will all shift the numbers.
In a single-file paceline at road-cycling speeds, the second rider sees about 27% less aerodynamic drag than a solo rider. Position 3 saves about 33%, and savings peak around positions 5–6 at roughly 38%. Translated to total power on a flat road, riders behind the leader typically save 20–35% of total watts. Drafting only helps with the air, so the rolling-resistance share of your power (~10–15% on a typical road bike) is unaffected.
When someone is sitting on the leader's wheel, the trailing rider creates a low-pressure bubble between the two cyclists which actually pushes the leader along very slightly. Blocken et al. (2018) wind tunnel and CFD studies put this bonus at around 3%. The rider on the front of a paceline isn't quite as exposed as a solo rider going the same speed.
The per-position drag-reduction percentages come from peer-reviewed wind tunnel and CFD studies on real and simulated pelotons (notably Blocken et al., 2018, on a 121-rider peloton). The aero/rolling power split assumes a representative 80 kg rider on the hoods with CdA ≈ 0.32 m² and Crr ≈ 0.005, which is typical for a club road cyclist. Real groups vary, heavier riders, fatter tyres, gusty wind, a wide gap to the wheel in front, or an aero position will shift the numbers by a few percent in either direction. The numbers should be in the right ballpark for planning purposes; treat them as estimates, not absolutes.
Aerodynamic power scales with speed cubed, while rolling resistance is linear in speed. So at 25 km/h, aero is roughly 60% of total power; at 45 km/h, it is about 87%. The same per-position drag-reduction percentage saves more absolute watts at higher speeds. This tool solves the group speed from the leader's wattage and applies the correct aero share for that speed automatically.
Yes, approximately. Wind tunnel and CFD studies treat the per-position drag-reduction ratio as roughly speed-invariant across the normal cycling range. There is a modest Reynolds-number effect (the absolute drag coefficient of an isolated cyclist drops about 20% from 20 km/h to 70 km/h), but the ratio between drafted and non-drafted drag stays nearly constant. The big speed-dependence in absolute watts saved comes from how much of total power is aero at that speed, which the model captures explicitly.
The last rider in a long single-file paceline doesn't get the trailing-wake bonus from someone behind them, so they save slightly less than mid-line riders. The model deducts ~2 percentage points from the per-position savings of the last rider in groups of 5 or more.
The model assumes a flat road. On steep climbs, more of your power goes to fighting gravity and less to fighting air, so drafting saves less in absolute terms. van Druenen & Blocken (2021) found that drafting at 6 m/s on a 7.5% gradient saves about 7% of power, versus roughly 25–30% drafting at the same speed on the flat. The savings come back at higher climbing speeds, at 8 m/s on the same gradient, savings climbed back to over 12%. Don't rely on this tool for power numbers on a sustained climb.
The single-file paceline numbers here are the foundation of team time trial pacing, the same physics applies. For specific TTT formations like staggered echelons or diamond patterns, savings can be greater still (a 4-rider diamond can drop the protected rider's drag to about 38% of solo). This tool only models single-file lines. If you're planning a TTT, use these numbers for the rotating-paceline portion and add a margin for the formation.
The model assumes still air or pure headwind. In a crosswind, riders form an echelon, offset to the leeward side of the rider in front, which has different aerodynamics. This tool doesn't model echelons. In a real crosswind on a single-file line, savings shrink substantially for any rider not directly behind the wheel in front.
Flat road, steady speed, single-file paceline, no crosswind, no traffic, ~1 m wheel-to-wheel gap. A representative 80 kg rider on the hoods with CdA ≈ 0.32 m² and Crr ≈ 0.005. All riders are assumed to share the same physical profile. Bigger gaps reduce drafting savings substantially, by more than 50% at gaps of 3 m or more.
Most cycling power calculators tell you how fast you'll go for a given power on a single-rider course (factoring aero, rolling, gradient, wind). This calculator does the inverse for a group: take the leader's effort as input and tell each rider behind what wattage they need to hold the wheel. It's built for paceline planning rather than solo time-trial pacing.
Yes, that's the main use case. Club rides, chain gangs, and through-and-off groups rotate the lead, so each rider takes shorter pulls at the higher wattage and longer stretches drafting in the line. Use this to figure out how hard you can pull on the front without blowing up before the next rotation, and how much rest you actually get sitting in.
No. All calculations and saved preferences run in your browser. Nothing is uploaded to any server.
Upload a GPX or pick a famous climb (Alpe d'Huez, Ventoux, Stelvio, Kona). Course-specific finish time, IF, TSS, race plan.
Research-based calorie estimator that accounts for climbing grade, wall angle, and rest time.
Chainring, cassette, and wheel into cadence vs speed. Gear ratio, gear inches, and development.
Estimate FTP from one max effort or fit critical power from several. Coggan 7-zone training zones, W/kg, power-duration curve.