Why a snake is predictable when a pile is not
A basket full of lit charcoal has an ill-defined number of briquettes burning at once, and that number climbs as the fire spreads through the pile. A snake constrains it. Only the briquettes at the burn front are alight, the front is one cross-section wide, and it advances at a speed set by how fast that cross-section is consumed. Change nothing else and the burn time is simply the total count divided by the hourly consumption.
That is what makes the arithmetic here worth doing at all. The geometry decides the count, and the count decides the hours, so a decision like whether to run 270 degrees or the full circle turns into a specific number of extra hours rather than a feeling.
The three levers, and which way each one pulls
| Change | Burn time | Pit temperature |
|---|---|---|
| Longer arc, or a smaller inset so the ring is bigger | Longer | Unchanged |
| An extra layer high | Longer at a fixed consumption rate; less in practice | Hotter |
| An extra briquette across | Longer at a fixed consumption rate; less in practice | Hotter |
| Vents open further | Shorter | Hotter |
| Smaller briquettes | More positions, similar total mass | Roughly unchanged |
The first row is the useful one: lengthening the run buys time without changing the fire. The two cross-section rows need reading carefully, and the calculator is explicit about which half it models. Adding a third layer to a two-layer snake puts half as much fuel again into the same run, so at an unchanged consumption rate the arithmetic says the burn runs half again as long — a snake at twelve hours twenty becomes eighteen and a half. But a wider or taller front has more briquettes alight at once, so the real consumption rate goes up too, and the true answer lands somewhere short of that. The page holds the rate you entered fixed and shows the fuel effect alone, which is why the line is labelled as a hotter fire front. If a snake is running too cool, the fix is the vents or the cross section; if it is running short, the fix is the arc.
Wood chunks are a schedule, not a quantity
Chunks laid along the snake deliver smoke on a timetable set by the burn front speed, not by anything you decide during the cook. Six chunks spread over a thirty-seven-inch run, with the front walking three inches an hour, sit just over six inches apart and put smoke into the chamber about every two hours through the burn, including the late hours when the meat has long since stopped taking on much colour. Bunching the chunks towards the lit end concentrates the smoke early, which is a real technique with a real geometric consequence, and the spacing figure on this page is what makes it visible.
Measuring your own consumption rate
Light a snake, run the kettle at the temperature you actually cook at with the vents where you actually set them, and after a measured two or three hours count the briquettes consumed — either by counting the ash positions or by counting what is left. Divide by the hours. That single number carries all the vent settings, all the weather and all the sealing quality of your particular kettle, and it is the only input on this page that a formula cannot supply.
Questions people ask
How long will a charcoal snake burn?
Total briquettes divided by the hourly consumption. A two-wide two-high snake running 270 degrees around a 22 inch kettle, set in 2.5 inches with a 3 inch break at the ends, is a 37 inch run: 37 positions at an inch each, four briquettes to a position, so 148 briquettes. At twelve an hour that is twelve hours and twenty minutes. Change the consumption rate to fifteen an hour and it is under ten. The rate is the sensitive input and it belongs to your kettle and your vent settings.
How many briquettes wide and high should a snake be?
That is a temperature decision rather than a duration one. More briquettes in the cross section means more burning at once, so a hotter fire that eats the snake faster. Two wide by two high is the common starting arrangement for a long low cook, and going to two by one runs cooler and shorter while two by three runs hotter. Use the arc length to buy duration and the cross section to set temperature.
Why does my snake burn faster than the calculation says?
Almost always because the consumption rate is higher than the one entered — vents further open than you think, wind, or a warm day. The second common cause is the fire jumping across the gap: if the snake curls back near its own start, or briquettes have rolled into the break, two fronts burn at once and the time halves. The gap field exists precisely to make that break a deliberate size rather than an accident.
Do I need a water pan with a snake?
It is a thermal mass and humidity choice rather than a fuel one, and this page has nothing to say about whether you want it. What it does affect for these purposes is the inset: a large pan pushes the snake outward towards the wall, which increases the radius and lengthens the run slightly. Measure the inset you can actually achieve with the pan in place and use that.
Does the brand of briquette change the numbers?
It changes two inputs and you can measure both. Footprint along the run sets how many positions fit in a given arc, and briquettes per pound sets weight and cost. Both vary between brands by enough to notice. What brand does not change is the structure of the calculation, and once you have measured your own footprint and your own consumption rate the answer is stable from cook to cook.