The job
Modelled, not recorded. Every figure on this page is re-run through the calculator it names whenever the site is built; the estimate is worked, but no job was carried out, so the last section gives the mechanism of each likely error rather than a measured overrun.
A gravel drive is bought as a load of stone and built as a stack of layers, and the stone on top is a small part of what goes into the ground. On this job the 20 mm gravel comes to under five tonnes (5.5 short tons); the open-graded stone beneath it weighs more than three times as much, and the soil that has to go before either arrives fills three lorries by volume. The steps below run in the order the work does, because each quantity is taken from the ground the step before it left behind.
The job: 6 × 10 m (19.7 × 32.8 ft) of gravel across the front of a house in England, replacing lawn, wide enough for two cars side by side. The build-up is 50 mm (2 in) of 20 mm angular gravel on 150 mm (5.9 in) of compacted clean 4/20 mm crushed stone over a separation geotextile — open-graded rather than Type 1, for the drainage reason set out below. A soldier course of 200 × 100 × 50 mm (7.9 × 3.9 × 2 in) concrete blocks, bedded and haunched in concrete, runs round all four sides outside the gravel. At the road end it marks the threshold, set level with the back of the footway, and the dig stops at the boundary so the footway itself is never opened.
THE LEVELS ARE FIXED BEFORE ANYTHING IS DUG. The gravel has to finish at least 150 mm (5.9 in) below the damp-proof course at the house end and no higher than the back of the footway at the other, so the fall between them is found rather than chosen, and the formation copies it 200 mm (7.9 in) lower. Every volume on the page hangs off that 200 mm: another 10 mm (0.4 in) across the 69.96 m² (753 sq ft) dig is 0.7 m³ (0.9 yd³) more soil out and as much stone back in.
THE DRAINAGE QUESTION COMES BEFORE THE ORDER. Under the Town and Country Planning (General Permitted Development) (England) Order 2015, a hard surface over 5 m² (54 sq ft) between the front of a house and the highway keeps its permitted-development status only if it is porous or its run-off is sent to a permeable area inside the boundary. The site's drainage guide is plain that loose gravel counts as porous only if what lies under it does too: over dense Type 1, water passing through the stone runs along the top of the sub-base to the lowest point, which on this drive is the footway. So the page models the porous route, with an open-graded sub-base in place of Type 1 over ground assumed to take the water. That assumption stands or falls on a timed-fill test in a hole at formation level. If the ground fails it, the choice becomes a filter trench along the road-end edge inside the boundary or a householder application, and neither is counted here.
WHAT THE PAGE LEAVES OUT. The drainage guide recommends setting the entrance metre or two of a front gravel drive in a cellular gravel grid, where wheels turn in off the road; the site has no calculator for that grid, so it is not counted. Nothing checks the planning condition or sizes the water the sub-base can store — that part is prose. The dropped kerb across the footway, which a new drive needs and the highway authority has to approve, lies outside the boundary and outside the count. The load count uses the dump-truck calculator's smallest tipper body as a stand-in for the grab lorry UK muck-aways are often booked on. The edge is counted on the paver calculator as a strip: the site's edging calculator counts spiked sections, and its notes leave open whether spiked edging is enough for a driveway, naming a concrete-haunched kerb or a soldier course as the usual restraint there. The concrete bed and haunch under and behind the blocks are not counted anywhere. Every figure shown comes from the calculator linked at its step; nothing here was dug or laid.
What was measured, and how
Finished levels at the house and at the footway
Gravel 150 mm (5.9 in) below the DPC at the house end; at the road end the gravel meets the soldier course flush, and that course sits level with the back of the footway, 200 mm (7.9 in) lower and 10 m (32.8 ft) along
The laser is set up once and read at the damp-proof course and again at the back of the footway with the lawn still in place, and both heights go on to pegs driven beyond the dig so a string between them survives the digging. Taking heights off the turf is the usual slip, because the turf is the first thing removed.
Plan size: gravel, edge and dig
Gravel 6.0 × 10.0 m (19.7 × 32.8 ft); edge 200 mm (7.9 in) wide plus 100 mm (3.9 in) for the haunch on every side; dig 6.6 × 10.6 m (21 ft 8 in × 34 ft 9 in), 69.96 m² (753 sq ft)
Set out with string lines for the gravel first, then the edge outside it, then the dig outside that. At the road end the outer dig line is the back of the footway, so the haunch fills the last 100 mm (3.9 in) inside the boundary. Digging only to the gravel line is the common error, because it leaves the edge blocks and their haunch standing on lawn beside the sub-base instead of on top of it.
Depth from the finished line to formation
50 mm (2 in) gravel on 150 mm (5.9 in) sub-base, fabric negligible: formation 200 mm (7.9 in) under the finished line, cut deeper under the edge for its concrete bed
Read off the string, never off the lawn. The 50 mm (2 in) of gravel rests on 150 mm (5.9 in) of compacted sub-base, the fabric beneath takes no depth worth counting, and the formation is trimmed to follow the string 200 mm (7.9 in) down. The slip that matters is forgetting the gravel and treating the sub-base as the surface: the formation ends 50 mm (2 in) high and the stone stands proud of the edge meant to contain it.
What lies under the lawn: services, topsoil and surface height
Lawn taken as sitting at the finished level along the whole fall, so the dig is a uniform 200 mm (7.9 in); topsoil taken to end within that depth; no service taken to lie shallower than the dig
A cable avoidance tool is walked over the whole frontage before any digging, since the water and gas supplies cross a front garden on their way in, the electricity often does too, and a shallow one can lie within 200 mm (7.9 in) of the surface. Heights are then read across the lawn every couple of metres in both directions, and a trial hole is opened at each end to find where topsoil gives way to firm subsoil. A scan done once the turf is off has already missed its purpose.
How fast the ground takes water at formation level
Not measured on a modelled page: the ground is assumed to take the water, which is what keeps this build on the porous side of the planning condition
A hole dug to formation level rather than spade depth, filled with water and timed as it drains, three times over, with the slowest result the one that counts — the timed-fill test the site's drainage guide describes. Testing the topsoil tells nothing, because the topsoil leaves in the lorry and the water has to go into what lies beneath it.
The takeoff, in order
Each step needs something from the one before it, which is why the order is part of the answer.
Fix the fall between the two levels that cannot move
- Needs
- The two fixed levels from the measurements — 150 mm (5.9 in) below the DPC at the house end, the back of the footway at the road end — and the 10 m (32.8 ft) of gravel between them, taken as a horizontal distance rather than along the lawn.
- Produces
- A 2% fall: enough to shed water, and far below the 15–20% the calculator's notes give as where a drive becomes hard to drive and park on, so the fall is not what moves the stone here; turning wheels are. The formation follows it 200 mm (7.9 in) lower, so any water the ground under the sub-base cannot take runs down the formation towards the footway — the fact the drainage decision turns on.
Result2% (1.15°): 200 mm (7.9 in) of fall over 10 m (32.8 ft)
Slope & Grade CalculatorTurn the dig into the volume that leaves site
- Needs
- The 200 mm (7.9 in) build-up measured down from the fall fixed in step one, across the 6.6 × 10.6 m (21 ft 8 in × 34 ft 9 in) dig: 13.99 m³ (18.3 yd³) of turf, topsoil and the top of the subsoil in the ground, at the calculator's default swell for common earth.
- Produces
- The loose volume once dug, a quarter larger than the hole it came from. All of it leaves, so the recompacted figure in the breakdown has no use on this job; the loose figure is the one the next step divides into loads.
Result17.5 m³ (22.9 yd³) of loose spoil
Soil Swell & Shrinkage Haul Volume CalculatorCount the loads the spoil makes
- Needs
- The 17.5 m³ (22.9 yd³) of loose spoil from step two — not the 13.99 m³ in the ground — set against the smallest tipper body in the calculator's menu, standing in for the grab lorry a UK muck-away is often booked on.
- Produces
- Three loads by volume. The count ignores weight, and topsoil lifted from a lawn can reach a payload limit before the body is full. A grab lorry taking spoil away can bring aggregate back on the return, which is worth asking for when the loads are booked, since step five needs a delivery.
Result3 loads of an 8 m³ tipper (3 of 10 yd³ on the imperial setting)
Dump Truck Load CalculatorLine the formation with separation fabric
- Needs
- The dug formation from step two, 6.6 × 10.6 m (21 ft 8 in × 34 ft 9 in), trimmed and rolled once the loads in step three have cleared it. The run is entered as 11.0 m (36 ft 1 in), 200 mm (7.9 in) past the dig at each end for a turn-up, with a roll 4.5 m (14 ft 9 in) wide and 100 m (328 ft) long and a 300 mm (12 in) lap between passes.
- Produces
- Two passes down the length with one lapped joint: 22.0 m (72.2 ft) of run, 99 m² (1,066 sq ft) laps included. A trade roll is far longer than this job, so the order is the cut length. The two widths cover 8.7 m (28 ft 7 in) against the 6.6 m dig, enough to turn the fabric up the long sides before the rest is trimmed.
Result1 roll: 22.0 m (72.2 ft) of 4.5 m (14 ft 9 in) fabric, 99 m² (1,066 sq ft) with laps
Driveway Separation Geotextile Roll CalculatorQuantify the open-graded sub-base
- Needs
- The fabric-covered floor of the dig from step four, 69.96 m² (753 sq ft) — the whole dig, so the edge course bears on sub-base rather than lawn, and not the turn-ups — at 150 mm (5.9 in) compacted and 1,600 kg/m³ (100 pcf) — near the loose weight of crushed stone, not the 2,200 kg/m³ (137 pcf) the calculator opens on for a dense-graded base, because clean 4/20 mm stone has no fines filling the gaps between its particles.
- Produces
- The compacted tonnage, the heaviest line on the page and more than three times the surface gravel. The 150 mm is a depth for cars; whether it also stores enough water is a storage and drain-down check that needs a measured infiltration rate and local rainfall, which this page does not have. Dense Type 1 at the same depth would weigh more — about 23 t (25.4 short tons) at the calculator's 2,200 kg/m³ — and it would undo the drainage. The 10.49 m³ (13.7 yd³) in the breakdown is the space the stone fills once compacted, not what the lorry tips.
Result16.8 t (18.5 short tons) of 4/20 mm open-graded stone, compacted
Gravel Base Layer Tonnage CalculatorSplit the sub-base into compaction lifts
- Needs
- The 150 mm (5.9 in) compacted depth from step five and the plate compactor on hire, taken here as compacting through about 100 mm (3.9 in) of finished layer at a time — a figure to check against the machine's own data. The calculator's lift field asks for the maximum loose lift; this page enters the compacted figure there on purpose, so both inputs are measured the same way and the ratio between them holds.
- Produces
- Two lifts of about 75 mm (3 in), each spread level and run over until the plate stops leaving a mark; clean stone has no fines to wet, so no water goes on first. Tipped as one layer, 150 mm gets a firm crust over a loose lower half, and the ruts that follow show in the gravel rather than in the sub-base where the fault lies.
Result2 lifts of about 75 mm (3 in) compacted
Backfill Compaction Lift Count CalculatorCount the blocks for the edge
- Needs
- The compacted sub-base from step six, which the edge's concrete bed sits on, and the edge entered as a strip: 32.8 m (107.6 ft) along its centre line and 200 mm (7.9 in) wide, in 200 × 100 mm (7.9 × 3.9 in) blocks laid as a soldier course.
- Produces
- About ten and a half blocks to the metre at the calculator's lowest cutting allowance. The centre-line strip counts the four corner squares correctly, since 32.8 m by 200 mm is exactly the frame between the 6 × 10 m gravel and the 6.4 × 10.4 m (21.0 × 34.1 ft) outer edge. The deeper dig along the edge line and the concrete bed and haunch in it are not counted here, and the haunch has to cure before stone is pushed against it.
Result345 blocks of 200 × 100 mm (7.9 × 3.9 in)
Paver CalculatorOrder the surface gravel
- Needs
- The 6 × 10 m (19.7 × 32.8 ft) enclosed by the cured edge from step seven — not the dig, since the sub-base under the edge carries blocks rather than stone — and a 50 mm (2 in) layer of 20 mm angular gravel over the sub-base from step five. The calculator's help gives 4–6 in (10–15 cm) as standard for a driveway; that is stone laid as the whole drive, whereas here the sub-base carries the cars and the gravel is only a wearing course, kept thin as the site's gravel guide advises.
- Produces
- The surface stone at the calculator's one fixed density, 1.4 short tons per cubic yard. It computes in US short tons, 5.49 here, and shows the figure on the metric setting as 4.98 t, spread as 3.0 m³ (3.9 yd³). The thinnest layer on the page, and the only one that is topped up for as long as the drive is used.
Result4.98 t (5.49 short tons) of 20 mm gravel
Gravel Driveway Calculator
The figures
| Step | Calculator | Figure |
|---|---|---|
| Fix the fall between the two levels that cannot move | Slope & Grade Calculator | 2% (1.15°): 200 mm (7.9 in) of fall over 10 m (32.8 ft) |
| Turn the dig into the volume that leaves site | Soil Swell & Shrinkage Haul Volume Calculator | 17.5 m³ (22.9 yd³) of loose spoil |
| Count the loads the spoil makes | Dump Truck Load Calculator | 3 loads of an 8 m³ tipper (3 of 10 yd³ on the imperial setting) |
| Line the formation with separation fabric | Driveway Separation Geotextile Roll Calculator | 1 roll: 22.0 m (72.2 ft) of 4.5 m (14 ft 9 in) fabric, 99 m² (1,066 sq ft) with laps |
| Quantify the open-graded sub-base | Gravel Base Layer Tonnage Calculator | 16.8 t (18.5 short tons) of 4/20 mm open-graded stone, compacted |
| Split the sub-base into compaction lifts | Backfill Compaction Lift Count Calculator | 2 lifts of about 75 mm (3 in) compacted |
| Count the blocks for the edge | Paver Calculator | 345 blocks of 200 × 100 mm (7.9 × 3.9 in) |
| Order the surface gravel | Gravel Driveway Calculator | 4.98 t (5.49 short tons) of 20 mm gravel |
The waste factors, and why these ends of the ranges
| Material | Applied | Why |
|---|---|---|
| Open-graded sub-base | The top of the calculator's suggested margin, added to the tonnage before the lorry is booked | Spillage and a dig that strays past its line are what the calculator's FAQ has in mind when it calls a margin of 5 to 10% reasonable, and it builds none in. On a lawn dug by hand the upper figure fits: the spade wanders wide of the string, soft spots show under the plate and get cut out, and stone rather than soil goes back into each of them. |
| Separation geotextile | The full cut run, lengthened for a turn-up at each end, with the surplus width turned up the long sides | The calculator carries the lap between the two passes, and two 4.5 m widths give 8.7 m against a 6.6 m dig, so the long sides have fabric to spare. Its notes leave turn-ups and anchor trenches outside the count, and the spare width does nothing for the two 6.6 m ends, so the run is entered 200 mm past the dig at each end: 11.0 m instead of 10.6 m, still inside one roll. |
| Edge blocks | The calculator's lowest cutting allowance, since a straight soldier course cuts only at the corners | Its minimum is 5%, which on the 328 blocks the strip needs is 17 spares once rounded. A rectangle of square corners asks for few cuts; the spares cover chipped arrises, a block that splits badly on the block splitter at a corner, and matching colour later. |
| Surface gravel | Nothing on the first order beyond rounding up to whole bulk bags or the supplier's minimum load | The first weeks of traffic press stone into the top of the sub-base and carry some away on tyres, so the layer thins. The calculator's notes treat replacing that as a topping-up cycle rather than part of the first quantity, and a margin bought now only sits in a heap until that cycle starts. |
| Spoil haulage | Booked on the loose volume in whole loads, then checked against payload | The 25% swell turns 13.99 m³ in the ground into 17.5 m³ in the body, and that is before weight is considered. Topsoil lifted in a wet month is heavy, so a haulier charging by the load may carry fewer cubic metres a trip than the body holds, and the count only rises from there. |
Where this estimate is most likely to be wrong
Dig depth and the spoil it makes
usually underThe 200 mm dig assumes firm subsoil at formation level and a lawn already at the finished line. Front-garden topsoil often runs deeper, and organic soil left under the fabric keeps compressing beneath the sub-base for years, so the dig follows it down; every extra depth across the whole 69.96 m² comes out bulked and goes into the lorry count. The deeper strip along the edge line for the concrete bed adds to the spoil again, and the computed dig leaves it out.
Narrow it by: Opening three pits down the centre line — by the house, halfway and at the footway — and reading the depth to firm subsoil in each before any lorry is booked.
Sub-base tonnage
usually underIt fills the formation as dug, not as drawn. Wherever the dig went deeper to reach firm ground the difference is made up in stone rather than soil, and the density used is the bottom of the calculator's range, so a quarry's 4/20 that compacts heavier pushes the delivered weight up again. A yard that sends Type 1 by default adds weight and removes the drainage in one delivery.
Narrow it by: Levelling the trimmed formation from the string lines before ordering, taking the compacted density of the named 4/20 product from the quarry, and checking the designation on the delivery ticket.
Whether the ground takes the water
usually underThe porous route modelled here holds only if the subgrade drains the open stone, and under a front garden of clay or made ground it may not. Every way out adds to the figures: a deeper sub-base to store more, a filter trench along the road-end edge inside the boundary, or a householder application whose drainage terms the council sets. The drainage guide also notes that BRE Digest 365 keeps infiltration clear of foundations, which bears on the house end of this drive.
Narrow it by: Timing three fills of a hole dug to formation level before any stone is ordered, and choosing the route on the slowest result rather than the fastest.
Surface gravel weight
either wayThe calculator holds one density for every stone, and 20 mm gravel from one quarry does not weigh the same as from another. Spreading it deeper than 50 mm to hide a patchy sub-base adds weight fast and makes the surface wander, while a merchant selling by the bulk bag sets the order in whole bags whatever the arithmetic says.
Narrow it by: Asking the supplier for the product's own weight per cubic metre and converting the 3.0 m³ spread with that figure.
Number of spoil loads
either wayTopsoil kept back for borders elsewhere in the garden never reaches the lorry and pulls the count down; wet spoil that meets a payload limit before the body is full pushes it up. The calculator counts volume only, and cannot see which of those two governs on the day.
Narrow it by: Deciding which soil stays on site before booking, and asking the haulier whether they load to weight or to volume.
Tools this job needs
Frequently asked questions
- How much gravel do I need for a 6 × 10 m driveway?
- At 50 mm (2 in) deep, 6 × 10 m (19.7 × 32.8 ft) of 20 mm gravel is 3.0 m³ (3.9 yd³), which the gravel driveway calculator puts at 4.98 t (5.49 short tons). That is only the top layer. Beneath it sit 16.8 t (18.5 short tons) of compacted open-graded stone, 150 mm (5.9 in) deep across the wider 6.6 × 10.6 m (21 ft 8 in × 34 ft 9 in) dig. Order the surface in whole bags or loads, and expect to top it up.
- What materials go into a gravel driveway?
- Listed as quantities rather than prices, since rates are local. For 6 × 10 m (19.7 × 32.8 ft) of gravel: 17.5 m³ (22.9 yd³) of loose spoil out in three loads, 99 m² (1,066 sq ft) of geotextile, 16.8 t (18.5 short tons) of open-graded stone compacted in two lifts, 345 edge blocks on a concrete bed, and 4.98 t (5.49 short tons) of surface gravel. The dig and the sub-base outweigh the visible stone several times over.
- Does a gravel driveway need planning permission?
- In England, a front hard surface over 5 m² (54 sq ft) between the house and the highway stays permitted development only if porous or draining to a permeable area inside the boundary. This drive covers 66.6 m² (716 sq ft) with its edge, and gravel counts as porous only over open-graded stone on ground that takes water. A new drive also needs the highway authority's approval for the dropped kerb, and on an A, B or C road a planning application whatever the surface. Wales and Scotland differ.