UK Sportive Difficulty Calculator
Explain like I'm 5
For cyclists, climbing speed is dictated by physics: power, gravity, and your weight. Drop in a GPX file for your sportive (or any planned route), tell the calculator what you weigh and how quickly you can ride on a flat road, and you'll get a realistic finish time, every categorised climb flagged, and the speed you'll likely hit on the biggest descent. Got a power meter? Enter your sustained ride power instead of speed, the maths is more direct.
Route summary
- Predicted finish time–
- Average speed–
- Sustained power–
- Difficulty rating–
- Total distance–
- Total ascent–
- Total descent–
- Ascent per km–
- Steepest climb gradient–
- Top descent speed (capped at 80 km/h)–
Categorised climbs
This route has no climbs that meet the Strava categorisation threshold (length × grade ≥ 8000). Either it's flat, or the climbs are short and punchy rather than long and steady.
| Climb | Length | Average grade | Ascent | Predicted arrival | Category |
|---|
Show workings
Why cycling time prediction is a physics problem, not a fitness one
For runners, terrain adjustment is mostly about metabolic cost: how much harder is it to run uphill at the same effort? For cyclists, it's about Newton's second law: how hard is the bike pushing back, and what speed makes the equation balance? At any given grade, your sustained speed is the speed where your power output exactly matches the work done against rolling resistance, aerodynamic drag, and gravity. That's a different model from the one we used for the marathon calculator, and it produces some genuinely surprising results.
The cycling-power equation is well-established physics. Power equals the sum of three forces multiplied by speed: gravity along the slope, rolling resistance from the tyres, and aerodynamic drag from the air you have to push out of the way. The first two scale linearly with speed; the third scales with the cube of speed. Cube. That's why doubling your speed from 20 to 40 km/h costs eight times more aero power, not two times. It's also why a strong cyclist who can go 35 km/h on the flat is suddenly the same speed as a weaker one on a 6% climb: gravity dominates, and at 12 km/h up a hill, aero is irrelevant.
The two effort inputs and which to use
If you have a power meter, enter your sustained power and ignore the speed field. The reading is direct: at 200 watts on a flat road in 1.225 kg/m³ air, with your CdA, your Crr, and your total mass, the bike will go a specific speed. Power gives the calculator the cleanest signal.
If you don't have a power meter, you do still have a sense of how fast you can keep going on a flat road for an hour. Most club cyclists settle around 25 to 32 km/h. Recreational riders sit lower. Racers go higher, and they're usually in the drops to do it. Tell the calculator your flat-road pace and it inverts the equation: it works out what power you must be producing to hold that speed at zero gradient with the rider-type defaults, and uses that power for the rest of the route.
The rider-type dropdown is the aero shortcut
Aerodynamic drag is the single largest variable above 25 km/h, and it's almost entirely a function of body position and equipment, not fitness. A rider sat bolt upright on the hoods has a CdA (drag area) around 0.40 m². A club rider down on the drops occasionally is around 0.32. A racer in the drops on aero kit is around 0.27. The same rider holding the same power produces wildly different speeds across that range.
If you don't know your CdA (almost nobody outside competitive racing does), the rider-type dropdown picks a sensible default for each archetype. The same dropdown also adjusts the rolling resistance coefficient: better tyres at higher pressures save real watts, and the gear most racers ride reflects that.
What this calculator is honest about
It assumes constant power. Real cyclists ramp power up on climbs and ease off on descents, especially long ones. The calculator's simplification is to apply your target power across all sections except descents steeper than -1.5%, where it switches to coasting (zero pedal power, terminal velocity governed by aero drag). That's broadly what experienced sportive riders do anyway: pedal hard up, pedal hard along, freewheel down, repeat.
It assumes still air. Wind direction relative to the course is the single largest unmodelled variable. A 20 km/h headwind on a flat sportive will cost you maybe 25% of your average speed; a tailwind for the same section will give it back. Neither is in a GPX file. If your race day forecast is brutal, treat the prediction as a calm-day baseline and adjust mentally.
It assumes you don't stop. Feed station time, route mistakes, mechanicals, and standing around at the start aren't in the model. Add 5 to 15 minutes of stop time per feed station depending on how civilised you are about it.
Why the descent speed is capped
Pure physics says a fit cyclist on a 12% descent can hit 90 km/h or more, and a few people do. In real life, on an unfamiliar sportive course with corners, traffic, gravel, and consequences, almost nobody does that and most shouldn't try. The calculator caps at 80 km/h, which is what a confident descender on a clean road might genuinely achieve. The number you see is what's plausible, not what the equations theoretically allow.
Where to find a GPX file
UK sportive organisers almost universally publish the official GPX or RouteYou link on the event page. If they don't, you can usually find a recent finisher's Strava activity (filter the segment leaderboard for that year's event, click any rider's activity, export GPX). Plotaroute, Komoot, RideWithGPS and Strava routes all export GPX. Save the file locally, drop it in here, hit calculate.
Related calculators
Course difficulty sets the target. These cover pacing and fuelling around it.
Common questions
What's a sportive?
A sportive is a mass-participation organised road bike ride, typically 50 to 200 km, with timed sections, feed stations, and a fixed route published in advance. Think of it as the cycling equivalent of a marathon: you're not racing for prize money, you're aiming for a personal time on a known course. Famous UK examples include the Fred Whitton Challenge, the Etape Caledonia, the Dragon Ride, and the Tour of the Peak District.
How does the calculator predict my finish time?
It uses the standard cycling-power equation: power output equals the work done against rolling resistance, aerodynamic drag, and gravity, plus drivetrain losses. From your inputs (weight, rider type, target flat-road speed or power), it works out the speed you can sustain at every point on the GPX trace and integrates the time. Climbs slow you down dramatically because gravity dominates; descents speed you up until aerodynamic drag catches up.
Should I enter speed or power?
If you have a power meter, enter your sustained power (typically 70 to 80% of your FTP for a long sportive). It's the more accurate input. If you don't have a power meter, enter the average speed you can hold on a flat road on a quiet day. The calculator will work backwards to figure out the equivalent power. If you supply both, power wins.
What does CdA mean and why does my rider type matter?
CdA is your drag area: the product of your frontal area and your drag coefficient. It's the single biggest variable above 25 km/h, because aerodynamic drag rises with the cube of speed. A rider sat upright on hoods has a CdA around 0.40 m². A club rider down on the drops occasionally is around 0.32. A racer in the drops on aero kit is around 0.27. The calculator picks sensible defaults from the rider-type dropdown. Crr (rolling resistance) varies less but also matters: better tyres at higher pressures save real watts.
Why is the descent speed capped at 80 km/h?
Pure physics says a fit cyclist on a 12% descent can hit 90+ km/h. In real life almost nobody does that on an unfamiliar sportive course, because the descent has corners, traffic, gravel, and consequences. 80 km/h is the calculator's safety ceiling: realistic for a confident descender on a clean road, the upper bound for what a sensible person would actually attempt. The number you see is what you'll plausibly do, not what the equations theoretically allow.
Why don't you apply a late-race fatigue penalty like the marathon calculator does?
Cyclists eat and drink on the bike. A sportive isn't a marathon: glycogen depletion is much less of a factor when you can refuel mid-ride at feed stations. There's no "wall" at km 80 of a 100km ride the way there is at km 32 of a marathon. For 200km+ audaxes that changes, but the typical UK sportive doesn't need a fatigue weighting and applying one would just make the prediction artificially pessimistic.