Cycling Wattage Calculator

This cycling wattage calculator is a tool designed for all cycling passionates. With its help, you can explore the relationship between the power you produce and various parameters such as speed, biking position, hill slope, or pavement type. For example, you can find out how much power you can save when switching from knobby to slick tires.

Thanks to this cycling power calculator, you will finally be able to compare two cyclists with fundamentally different styles — for example, a road cyclist who never gets off his slick-tired bike and an MTB enthusiast who enjoys hardcore off-road adventures.

Cycling wattage is the power you produce with your legs to get your bike going (and, preferably, going fast). You can think of it as the ultimate measure of your biking skills: the more power you can produce, the better cyclist you are.

The cycling power is measured in watts. One watt corresponds to one joule of energy produced every second.

Our cycling wattage calculator is based on the model described in detail in the paper "What is slowing me down? Estimation of rolling resistances during cycling". It assumes that the power you produce is equal to the sum of resistances you need to overcome, multiplied by your speed. Additionally, we take power losses into consideration.

The cycling wattage formula that we use looks like this:

where:

• $P$ — Your power;
• $F_\mathrm{g}$ — Resisting force due to gravity;
• $F_\mathrm{r}$ — Rolling resistance force;
• $F_\mathrm{a}$ — Aerodynamic drag;
• $v$ — Your speed in m/s; and
• $\text{loss}$ — Percentage loss in power.

In the following sections of this text, we will look at each component of this cycling power equation in more detail.

If you're cycling uphill, you need to overcome the force of gravity. Naturally, if you're going downhill, gravity will actually help you, making you accelerate without any additional effort.

The force of gravity can be calculated as follows:

where:

• $F_\mathrm{g}$ — Resisting force due to gravity;
• $g$ — Gravitational acceleration, equal to $9.80665\ \text{m}/\text{s}^2$;
• $\text{slope}$ — Slope of the hill, expressed as a percentage (positive for going uphill and negative for going downhill);
• $M$ — Your weight in kg; and
• $m$ — Weight of your bicycle and any extra gear, also in kg.

The next factor that will undoubtedly slow you down is the friction between your tires and the surface (see the friction calculator). The smoother the road and the slicker your tires, the less friction you will experience.

The formula for rolling resistance is:

where:

• $F_\mathrm{r}$ — Rolling resistance; and
• $C_\mathrm{rr}$ — Rolling resistance coefficient.

The estimates for the rolling resistance coefficient $C_\mathrm{rr}$ in our cycling wattage calculator are based on the findings of researchers from the University of Pretoria and the University of Reims Champagne Ardenne:

The third component of the power equation is the aerodynamic drag. It's a force of air resistance. Unlike the previous two components, it's dependent on your speed raised to the second power – the faster you are, the higher the air resistance. It means that the faster you go, the more difficult it is to keep speeding up.

The aerodynamic drag can be calculated according to the formula below:

where:

• $F_\mathrm{a}$ – Aerodynamic drag;
• $C_\mathrm{d}$ – Drag coefficient;
• $A$ – Your frontal area;
• $\rho$ – Air density;
• $v$ – Your speed; and
• $w$ – Wind speed (positive for headwind and negative for tailwind).

It is common to estimate the value of $C_\mathrm{d} \times A$ instead of determining each of these two separately. We are using the values suggested by Asker E. Jeukendrup in his book "High Performance Cycling":

The positions are:

• Tops – Hands hold the top straight portion of the handlebars.
• Hoods – Hands grip the brake lever hoods at the top of the curved portion of the handlebars.
• Drops – Hands hold lower down the curve on the dropped or curved section of the handlebars.
• Aerobars – Hands grip the extra handlebars on the front of the triathlon bike.

Additionally, our cycling wattage calculator estimates the air density at a given elevation above sea level (a.s.l.) according to the barometric formula:

where:

• $\rho$ – Air density;
• $\rho_0$ – Air density at the sea level, equal to $1.225\ \text{kg}/\text{m}^2$;
• $M_0$ – Molar mass of Earth's air, equal to $0.0289644\ \text{kg}/\text{mol}$;
• $h$ – Elevation above sea level;
• $R$ – Universal gas constant for air, equal to $8.3144598\ \text{N×m}/\text{(mol×K)}$; and
• $T_0$ – Standard temperature equal to $288.15\ \text{K}$.

After substituting the constants, we can simplify this equation to:

Not all of the power that you produce when cycling is transferred directly to the wheels. Some of it is lost either due to the resistance of the chain or of the derailleur pulleys.

Our cycling power calculator assumes a constant 1.5% loss on your pulleys. The losses on the chain are dependent on its condition:

• $3\%$ for a new, well-oiled chain;
• $4\%$ for a dry chain (for example, when the oil has been washed away by rain); and
• $5\%$ for a dry chain that is so old it became elongated.

You can check out this article on the mechanical resistance of bikes for more information about power losses.

Now you know your cycling wattage – but what does that number mean, exactly? The table below provides an overview of the power-to-weight ratio (power that can be produced per kilogram of body weight) over different durations compiled by Dr. Andrew Coggan, a renowned exercise physiologist.

For a cyclist, power is probably the most useful piece of data you can get. By knowing your power, you can learn about your performance, health, and even the state of your body. Of all of these values, the most mainstream of them has to be calorie consumption.

Not only are calories a common way for people to measure the level of activity they perform, but it also helps you better plan your nutrition and provides a measure by which you can set goals, be it fat loss, performance improvement, or building muscle.

It is for this reason that we have added Energy Consumption section, that lets you estimate the calories you burnt on your ride. This is a very simple process since power and energy are related by a single value: elapsed time.

When we are talking about a human doing some work, we also need to take into account the inefficiencies of our bodies. Our bodies always burn more energy than they produce and that difference is what we call efficiency (see the efficiency calculator). Once we model these losses into our formula, we arrive at the following:

Here $\small\text{Power}$ refers to the average power you sustained for the $\small\text{Time}$ of the activity, $4.18$ is the conversion factor from Joules (SI unit) to calories, and $0.24$ is the efficiency ($24\%$) of an average human body when cycling.

Remember that this is an estimation that works better for steady-paced rides than it does, for example, for HITT training. This is because the efficiency of our bodies changes slightly with power output and effort level.

If you want a more detailed analysis of your calorie consumption on the bike and the fat-loss implications, please visit our calories burned while cycling calculator.