Every number, in one table
The whole set, with units, without the prose around it. Every value here is read out of the same table the engine is tested against, so it cannot disagree with the game.
Last updated 2026-08-18
How to read this#
Two kinds of number appear on this page and they are not the same kind of thing.
- Rules are limits set by World Curling. A stone may weigh between 38 and 44 pounds. That is a range, and every stone in the world sits somewhere inside it.
- Measurements are the particular values this simulator uses, taken from a representative stone and a regulation sheet. They sit inside the rules, and they are what every other number here is computed from.
Where the two differ, both are given. Conflating them is how "a curling stone weighs 19 kg" turns into a rule that it must, which it is not.
Every position on this site is given as feet from the hack the stone was thrown from, because that is the frame the whole engine works in and it makes the weight tables read as positions rather than as offsets from something else. The far button is at 126 ft.
The sheet#
| Landmark | Feet from the hack | Metres |
|---|---|---|
| Delivering hack | 0 | 0.000 |
| Near back line | 6 | 1.829 |
| Near tee line | 12 | 3.658 |
| Near hog line — release by here | 33 | 10.058 |
| Far hog line — must cross this | 105 | 32.004 |
| The button | 126 | 38.405 |
| Far back line | 132 | 40.234 |
| Far hack | 138 | 42.062 |
| Backboards | 144 | 43.891 |
| Dimension | Value | Note |
|---|---|---|
| Overall length | 150 ft (45.720 m) | May be reduced to 146 ft (44.501 m) in an existing building. |
| Width | 14 ft 6 in (4.420 m) | Rule R1(a) allows a maximum of 4.750 m (15 ft 7 in), reducible to this minimum where an existing building cannot take the full width. This simulator draws the minimum — see the note below. |
| Tee line to tee line | 114 ft (34.747 m) | Rule R1(b): each tee line is 57 ft from the middle of the sheet. |
| Hog line to tee line | 21 ft (6.401 m) | Measured to the inside edge of the hog line. |
| Tee line to back line | 6 ft (1.829 m) | To the outside edge. |
| Hog line width | 4 in (102 mm) | The only wide line on the sheet, which is why it is the visible one. |
| Centre line beyond the tee | 12 ft (3.658 m) | It runs on past the house to the hack line. |
| Courtesy lines | 4 ft (1.219 m) outside each hog line | Where the non-delivering team stands. |
| Hack separation | 3 in (76 mm) either side of centre | And no more than 6 in (152 mm) wide each. |
Rule R1(a) gives a range rather than a number: 4.750 m wide, reducible to 4.420 m where the building will not take it. This simulator draws the 4.420 m minimum. The width decides one thing only — how much room a stone has out to the sides before it is out of play — and the narrowest legal sheet is the least forgiving one to have learnt on, so a shot that stays in play here stays in play anywhere. Every other distance on this page is measured along the sheet and does not move with it.
The house#
| Ring | Radius, feet | Radius, metres | Colour, conventionally |
|---|---|---|---|
| Twelve-foot | 6 | 1.829 | Blue |
| Eight-foot | 4 | 1.219 | White |
| Four-foot | 2 | 0.610 | Red |
| Button | 0.5 | 0.152 | White |
Rings are named for their diameter, not their radius — the twelve-foot is six feet from the centre. The button's regulation minimum radius is 6 in, so it is a foot across.
The stone#
| Property | This simulator | World Curling limit |
|---|---|---|
| Mass | 19.0 kg | 17.24–19.96 kg (38–44 lb), handle and bolt included |
| Radius | 142 mm (diameter 284 mm) | Circumference no greater than 914 mm |
| Height | 114.5 mm | No less than 114 mm |
| Running band radius | 65 mm | Not specified in the rules |
| Running band width | — | Not specified; in practice 6–13 mm |
| Coefficient of restitution | 0.94 | Not specified — measured |
| Moment of inertia factor | 0.385 × M R² | Not 0.5: the mass sits low and inward |
The numbered weights#
The scale curlers call weight on, on the calibration sheet. Positions, not a linear scale — explained on calling weight by number.
| Called | Finishes at | Feet from hack | Release speed | Hog to hog |
|---|---|---|---|---|
| 1 | a deep guard | 111 | 2.019 m/s | 16.48 s |
| 2 | a guard | 114 | 2.056 m/s | 15.58 s |
| 3 | a tight guard | 117 | 2.091 m/s | 14.87 s |
| 4 | the top of the house | 120 | 2.126 m/s | 14.27 s |
| 5 | the top of the eight-foot | 122 | 2.149 m/s | 13.92 s |
| 6 | the top of the four-foot | 124 | 2.172 m/s | 13.60 s |
| 7 | the button | 126 | 2.194 m/s | 13.31 s |
| 8 | the back of the four-foot | 128 | 2.216 m/s | 13.04 s |
| 9 | the back of the eight-foot | 130 | 2.238 m/s | 12.78 s |
| 10 | the back line | 132 | 2.26 m/s | 12.55 s |
The named weights#
The other system, mostly for takeouts. Distances past the end of the sheet are where the stone would stop if it hit nothing — see why the weights are called what they are.
| Weight | Feet from hack | Release speed | Hog to hog |
|---|---|---|---|
| 1 Guard | 109 | 1.995 m/s | 17.27 s |
| 2 Guard | 113 | 2.043 m/s | 15.86 s |
| 3 Guard | 119 | 2.114 m/s | 14.46 s |
| Tee | 126 | 2.194 m/s | 13.31 s |
| Back Line | 132 | 2.26 m/s | 12.55 s |
| Hack | 138 | 2.324 m/s | 11.93 s |
| Board | 144 | 2.386 m/s | 11.40 s |
| Control | 175 | 2.681 m/s | 9.54 s |
| Normal | 198 | 2.879 m/s | 8.65 s |
| Peel | 274 | 3.448 m/s | 6.91 s |
The three sheets#
| Sheet | Friction | Curl | A button delivery stops at | Its own button draw | and reads |
|---|---|---|---|---|---|
| Club | ×1.10 | ×1.0 | 117.5 ft | 2.295 m/s | 12.72 s |
| Normal | ×1.00 | ×1.0 | 126.0 ft | 2.194 m/s | 13.31 s |
| Championship | ×0.85 | ×1.6 | 142.4 ft | 2.032 m/s | 14.37 s |
Read the last two columns together: keener ice needs a gentler throw to finish in the same place, so it reads a longer split. That is the whole of "fast ice, slow watch", and you can drag it on the draw simulator.
Physical constants#
Friction#
μ(v) = 0.00662 + 0.00231 / √vFriction rises as the stone slows. A constant coefficient cannot produce a correct hog-to-hog split and a correct total distance at once, which is the single most consequential modelling decision on this site.
Curl#
v_lateral = (β / 2) · v · ln(v₀ / v), β = 0.151Back-loaded: about 15% of the curl in the first half of the slide. Integrates to roughly a metre of deflection on a draw to the button. Why this shape, and why it is an engineering choice rather than a claim about nature, is on why a curling stone curls.
Sweeping#
| Constant | Value | What it is |
|---|---|---|
| Friction multiplier | 0.934 | Full-effort brushing, a 6.6% reduction. Measured, not tuned. |
| Fully effective below | 0.5 m/s | Slower than this and sweeping does everything it can. |
| Useless above | 1.5 m/s | Faster than this and the strokes no longer cover the ice in time. |
| Sideways displacement | 71 mm | From sweeping one half of the path over a 30 m draw — and it pushes the stone away from the swept side. |
| Brush head width | 0.2 m | Which is why the speed limits above exist. |
| Stroke rate | 4 per second | What a person can actually hold under load. |
Release#
| Constant | Value | What it is |
|---|---|---|
| Release point | 33 ft from the hack | The stone is carried to the hog line at constant speed and released there. Friction starts here, not at the hack. |
| Typical rotation | 2–5 turns over the sheet | Curl is essentially flat across this range, which is why the handle is a two-way switch. |
| Spin transferred in a collision | 0 | The standard modelling choice, and why a struck stone runs straight. |
Sources#
- Primary The Rules of Curling, R1 and R2 World Curling, 2025Every figure in the “World Curling limit” columns, and the sheet dimensions given in metres.
- Why a curling stone curlsWhere the curl law comes from, and why it is presented as a fitted engineering choice rather than as physics.
- What sweeping doesThe published measurements the sweeping constants are taken from.