Inside the kerb a standard 400 m track holds 10,346 m², or 85 rolls of 5 × 25 m with rolls laid across the 73 m width.
That area is running track infield turf, and it is not the 84.39 by 73 m rectangle, which holds only 6,160 m². The other 4,185 m² lies in the two D-ends, past the straight sides. Measure the kerb line before you price the job, because the rectangle and the infield are different orders. We cut rolls to the layout on the drawing, so the count follows the shape rather than a rule of thumb.
How Much Turf a 400m Infield Takes
Most quotes start from the rectangle. A standard 400 m track runs 84.39 m along each straight and 36.50 m around each bend, so the rectangle between the bend centres measures 84.39 by 73 m. That rectangle holds 6,160 m², while the full infield holds 10,346 m².
The gap is the two D-ends. Each semicircle covers 2,093 m², so the pair comes to 4,185 m² that no rectangle includes. Ordering from the rectangle leaves those ends unrolled, and a second production run is how the shortfall gets fixed.
- Inside the kerb: 10,346 m², the running track infield turf area used here.
- Rectangle between bend centres: 6,160 m², less than the 7,140 m² football pitch it has to hold.
- Outer edge of the track: 16,370 m², the whole oval footprint including the running surface.
Roll count follows the same split. On 5 m rolls the infield needs 85 rolls with rolls laid across the 73 m width; on 4 m rolls it needs 108. Both figures cover the full infield, D-ends included.
Measure to the kerb, not to the white line and not to the outside of the track. The kerb is the inner edge, and every area above is built from it. Lane one is measured 0.30 m outside the kerb, and the running surface reaches 9.76 m beyond it on each side. That offset is why the measured line and the kerb line are two different lengths.
The track surface and the infield are separate orders. The count here covers only the turf inside the kerb, and the running surface is priced with its own package.
The 84.39 m straight and the 36.50 m radius are set out in the World Athletics Track and Field Facilities Manual, as transcribed in this state government dimensions guide. Those two distances are the only inputs behind every area below. The manual fixes track geometry rather than infield surface, so the turf build is a separate brief.
Why the Infield Is 10,346 m², Not a Rectangle
The rectangle figure some quotes still use is 6,132 m², and it describes only the straight-sided middle. The kerb runs 398.116 m around the full inner edge, so the running track infield turf forms a stadium shape rather than a box. Both halves have to be measured before a roll count means anything.
Total length is 157.39 m: 84.39 m of straight plus 36.50 m of bend at each end. The width across the middle is 73 m. Those two numbers set every area that follows.
The Rectangle Between the Bend Centres
The rectangle runs 84.39 m by 73 m, which is 6,160 m². Its four corners sit on the centre line of each bend, so the rectangle stops where the curve begins.
The Two D-Ends
Each D-end is a semicircle of 36.50 m radius, so one end covers 2,093 m² and the pair covers 4,185 m². The arc sits 36.50 m from the bend centre at every point, which is why a straight band cannot follow it.
Add the parts and the infield comes to 6,160.5 + 4,185.4 ≈ 10,346 m², precise 10,345.86.
A 105 by 68 m football pitch takes 7,140 m² of that, leaving 3,206 m² spare. Nearly all of the spare land sits in the D-ends, so they are layout space rather than leftover ground.
At 68 m wide the infield gives 110.94 m of usable length, because the chord at 34 m from the centre line still clears the kerb. That leaves 2.97 m at each end of a 105 m pitch, which is why the pitch fits with almost nothing to spare.
The geometry comes from the World Athletics Track and Field Facilities Manual, whose 36.50 m radius and 84.39 m straight appear in World Athletics documentation and in national facility guides.
What the Outer Edge Adds
The outer edge of the running surface sits 9.76 m beyond the kerb on each side. The full oval measures 176.919 by 92.529 m, or 16,370 m². Quoting that instead of the infield overstates the running track infield turf order by 6,024 m².
Where the Turf Stops at the Kerb
The 10,346 m² already ends at the inner face of the kerb, so do not deduct the kerb again. It is a raised edge 0.05 m to 0.065 m high and 0.05 m to 0.25 m wide, and the turf butts against its inner face.
If the design puts a drainage or trim strip inside the kerb, that strip does come out of the order. Every 50 mm of width removes 19.9 m² along the 398.116 m perimeter. A strip at the 0.25 m maximum removes 99.5 m², so the deduction cannot exceed that figure.
Height matters more than area. Turf above the kerb top is a trip edge on the inside lane, and turf below it holds water at the low point. That detail belongs on a node drawing, not in a square metre figure.
Do not deduct the kerb twice. The 10,346 m² already stops at its inner face, and only a strip added inside that face changes the count.
Cross fall follows the track. A 1% fall toward the inside is the usual convention, and the infield has to meet that plane rather than find its own level. On a resurfaced track the existing falls decide how much edge trim the turf needs.
The track side of the kerb is a separate package, and where the artificial track surface ends is settled in that package rather than in this one.
What the Throw and Jump Zones Remove
Two kinds of hard surface sit inside the kerb, and only one of them is fixed. Sand pits and throwing circles are permanent, so they always come out of the turf area. Runways depend on the design.
The fixed group is small. Two landing pits at 9 by 2.75 m take 49.5 m², and three throwing circles of 2.135 m and 2.50 m diameter take 12.1 m². Together they remove 62 m², which is less than one 5 m roll.
The runway group is where the argument starts. Three 40 by 1.22 m runways and one 30 by 4 m javelin runway total 266.4 m². That strip is either turf or a synthetic rubber surface, and the choice is made at design stage. A school may turf all four runways, while a stadium built for competition usually lays them in rubber.
- Landing pits: 49.5 m², always excluded.
- Throwing circles: 12.1 m², always excluded.
- Runways in turf: 266.4 m² stays in the order.
- Runways in rubber: 266.4 m² comes out of it.
- Net running track infield turf: 10,018 to 10,284 m², depending on that choice.
The pits and circles are small enough to drop from a budget and too important to drop from a drawing. Runways are the reverse: easy to overlook, and large enough to force a second order.
The SAI field-of-play handbook lists 40 m by 1.22 m runways, a 30 m by 4 m javelin runway, and circles of 2.135 m and 2.50 m.
High jump is the trap. Its 20 m figure is the radius of a semicircular approach run, not the size of a landing sector, so it cannot be multiplied out into an area. A radius is not a sector dimension, so it cannot be converted into square metres at all.
Nothing here says a standard infield has two pits or one javelin runway. The layout is project-specific, which is why the drawing decides the deduction, and how much artificial turf you need covers the general measuring step.
How Radius Changes Area and Roll Count
A 400 m track is always 400 m, but the radius is not fixed. Recommended bend radii run from 35 m to 38 m, with 36.50 m treated as the optimum.
The straight length absorbs the difference. With the measurement line set 0.30 m outside the kerb, the straight is (400 − 2π(r + 0.30)) ÷ 2. The area is the straight length times the infield width, plus πr² for the two bends.
| Bend radius | Straight | Infield area | 5 m rolls, laid across the 73 m width |
|---|---|---|---|
| 35 m | 89.10 m | 10,086 m² | 86 |
| 36.50 m | 84.39 m | 10,346 m² | 85 |
| 38 m | 79.68 m | 10,592 m² | 102 |
At 35 m the infield holds 10,086 m² and needs 86 rolls; at 38 m it holds 10,592 m² and needs 102. The area moves 506 m², or 4.9%.
The roll column is the surprise. Area rises 4.9% across the band, yet the count jumps from 86 to 102.
Why 75 m Decides More Than Area
Rolls are 25 m long, so a 73 m wide infield needs three lengths across and a 76 m wide infield needs four. That single extra row is why the 38 m option jumps.
Width decides, not area. Two infields with the same square metreage can need different counts if one crosses 75 m, and the difference shows up as material rather than as a rounding error.
Read the radius first, then the area. A quote built from area alone cannot tell you which side of 75 m the infield sits on.
Why 84.39 Metres Makes Four Segments
Roll length is the constraint. Every standard roll is 25 m long, so the question is how many whole rolls cover 84.39 m and how many cover 73 m.
Along the straight the answer is four. 84.39 m runs past the third 25 m roll. A roll cannot arrive as a part piece, so each lane needs four segments.
Laid Along the Straight: 60 Rolls
Fifteen lanes at 5 m each span the 73 m width. Four segments per lane gives 60 rolls, or 7,500 m² of running track infield turf against a 6,160 m² rectangle.
Laid Across the Width: 51 Rolls
Turned through 90 degrees, the 73 m width runs past the second 25 m roll, so three lengths cover it. The 84.39 m length then needs 17 lanes, so the rectangle takes 51 rolls and 6,375 m².
The difference is nine rolls and 1,125 m² on the same ground with the same carpet. Direction produced it, not area.
Offcut length explains why. A straight-laid lane leaves 15.61 m of every fourth roll unused, and a cross-laid lane leaves 2 m. The short offcut is still a full 25 m piece, which is why the saving appears in the count rather than in the waste skip.
One rule survives either choice: pile direction must run the same way across the whole infield. Two adjacent lanes laid in opposite directions read as a colour band under floodlights, and no amount of brushing hides it.
Adding Two D-Ends to the Count
The D-ends cannot be cut as rectangles. Each semicircle covers 2,093 m², which becomes a 418.5 m strip at 5 m wide, and 418.5 ÷ 25 rounds up to 17 rolls. Two ends therefore add 34 rolls.
The rectangle takes 51 rolls across the width and the two ends take 34, so the infield needs 85 rolls with rolls laid across the 73 m width. That order covers 10,625 m², which is 279 m² above the 10,346 m² gross area, or 2.7%.
This is an arithmetic floor, not a cutting plan. Arc trims waste more than straight cuts and seams take a little extra, so a real order sits above that floor. Arc cutting has no fixed yield, which is why the figure is a floor rather than a forecast. A cricket outfield carries the same arc penalty, because its boundary curve drives the order the same way.
- 5 × 25 m: 85 rolls with rolls laid across the 73 m width, 10,625 m², 2.7% above the gross area.
- 4 × 25 m: 108 rolls, 10,800 m², 4.4% above it.
- 2 × 25 m: 213 rolls, 10,650 m², 2.9% above it.
Roll width changes handling more than tonnage. Wider rolls cut the piece count and the seam metres, while 2 m rolls suit narrow strips and top-ups rather than a whole infield.
Laid straight along the 84.39 m straight, the same infield needs 60 rolls for the rectangle plus 34 for the two D-ends, 94 rolls in total. That is nine more than the cross-laid count, and it is the number to avoid when the site allows either direction.
The general division for a plain rectangle sits in how many rolls of artificial grass; an infield adds the D-ends and the 75 m width check to that sum.
Infield Use Sets Pile and Infill
Pile height follows the use, not the shape. For running track infield turf, the warm-up case takes a short 12 mm carpet at 52,500 tufts per square metre. Grip there comes from density rather than fibre length.
An infield that also hosts football needs 50 mm, inside a 40 mm to 60 mm football range at 10,500 tufts per square metre. Ball roll and landing comfort both depend on that length.
Throw landings are a third case. A denser, harder build suits impact, and the exact figure belongs to the chosen system rather than to a general figure.
- Warm-up only: 12 mm, 52,500 tufts per square metre.
- Football or multi-sport: 50 mm, 10,500 tufts per square metre.
- Throw landings: denser build, set with the event layout.
- Backing: PP with non-woven, optional PU coating, perforated for drainage.
Infill is a tonnage question. At 20 to 30 kg per square metre of silica sand, 10,346 m² takes 207 to 310 tonnes. Performance infill at 8 to 15 kg per square metre adds 83 to 155 tonnes.
The athletics track turf specification carries the 12 mm build, the three-layer backing and the 50 mm option in one place. A shock pad suits warm-up zones, while throw landings want a firm response underfoot.
Ordering from the rectangle again?
The infield drawing carries the kerb line, radius and runway positions; we cut roll width and length to that layout, so the count matches the D-ends.
Infield Variables That Resize the Quantity
Nine inputs move the order, and none of them is a unit rate. That is why the work cannot be priced from a rate per square metre, and why two quotes for the same track often disagree.
- Area basis: measuring the rectangle instead of the kerb line changes the order by thousands of square metres.
- Runway surface: turf or rubber moves 266.4 m² in or out.
- Roll direction: straight or across the width changes the rectangle from 60 to 51 rolls.
- Bend radius: 35 m to 38 m moves the count from 86 to 102.
- Roll width: 5 m, 4 m or 2 m changes the piece count and the handling weight.
- Pile height: 12 mm or 50 mm changes the carpet, the density and the infill.
- D-end cutting: arcs produce more offcut than straight lanes on the same area.
- Kerb edge: a strip added inside the kerb deducts 19.9 to 99.5 m².
- Phasing: a second production run risks a batch colour difference in one D-end.
The first two dominate. The area basis decides whether the D-ends exist in the order at all, and the runway surface decides 266.4 m² on its own.
A quote that leaves either question open cannot be compared with another quote. Once both are fixed, the roll count is settled and the only variable left is the carpet itself. Two buyers can hold the same drawing and still order different quantities if one answers those questions late.
The Drawing That Prices an Infield
Ten items on one drawing settle the running track infield turf order. The first fixes the square metres, and the fifth fixes the 266.4 m² swing.
- Net dimensions inside the kerb, as length by width; a standard infield is 157.39 by 73 m.
- Bend radius and straight length, 36.50 m and 84.39 m or the surveyed values.
- Kerb profile, 0.05 m to 0.065 m high, plus any strip inside it.
- Throwing circle centres and diameters, 2.135 m and 2.50 m.
- Runway count, length and width, with the surface for each: turf or rubber.
- Landing pit outline, at least 2.75 m wide.
- Levels and fall direction, including the cross fall to the kerb.
- Infield use: warm-up, football, or both.
- Inlaid lines: which markings are woven in, and at what width.
- Phasing: one production run or a reserved top-up.
With those ten, a factory can draw the roll layout and count the rolls without a second round of questions. Without them, the layout is an assumption on both sides.
The last item is the one buyers drop. A top-up ordered months later may not match the first batch, and a colour difference in a D-end is hard to hide.
Frequently Asked Questions
How many square metres of turf does a 400 m track infield need?
Inside the kerb a standard 400 m infield needs 10,346 m² of running track infield turf. Sand pits and throwing circles remove 62 m², and runways remove up to 266.4 m² more.
How many rolls is that?
85 rolls of 5 × 25 m with rolls laid across the 73 m width, covering 10,625 m². Laid along the straight, the rectangle takes 60 and the D-ends 34, so 94 rolls. In 4 m rolls, 108.
Is the infield a rectangle or a D shape?
A D shape. The infield is a stadium: a 6,160 m² rectangle between the bend centres, plus two semicircles of 2,093 m² each, 157.39 m long overall.
Do throwing circles and runways come out of the turf?
Circles and pits always do: 62 m² in total. Runways come out only if they are laid in rubber; in turf they stay, and the deduction is 266.4 m².
Can 25 m rolls run along the 84.39 m straight?
Yes, at four segments per lane, because 84.39 m needs more than three 25 m rolls. Across the width each lane needs three segments, which saves nine rolls and 1,125 m².
What pile height if the infield also hosts football?
50 mm, inside the 40 mm to 60 mm football range. A warm-up-only infield takes 12 mm at 52,500 tufts per square metre.
