Compacted vs Loose Asphalt: Rolldown, Yield and What You Actually Order
A paver never lays a mat at its finished thickness — it places hot mix loose, taller than spec, and rollers consolidate it down to the compacted depth the plans call for. That gap is the rolldown, and it is where most asphalt quantity confusion starts: how much thicker is the loose mat, why do published numbers disagree, and — the question that actually costs money — which depth do you order tons against? This guide works the rolldown math from the Asphalt Paving Handbook, reconciles the two competing conventions behind the "25 percent" you see quoted, and shows why compaction never changes the tonnage you buy.
Short answer
Loose asphalt is thicker than compacted asphalt by the rolldown factor — about 25% for a typical dense-graded mix and about 15% for gap- or open-graded mixes (Asphalt Paving Handbook §7-5). Under the Handbook's own reading, a 2-inch compacted lift is placed 2.5 inches loose (2 × 1.25), and a 3-inch lift is placed about 3.75 inches loose. Crucially, rolldown changes thickness, not weight: you order tons from the COMPACTED volume × the material density, and the loose lay depth is only the screed setup number. The single markup on an order is a one-time waste allowance — never a compaction factor stacked on top.
Loose and compacted are the same tons, different thickness
Start from conservation of mass, because it settles almost every rolldown argument. The tons of hot mix that leave the plant and go into a lift do not change when the roller passes over them. Rolling squeezes air out of the mat: the same weight occupies less volume, so the mat gets thinner and denser. Nothing is added and nothing (but waste) is lost.
That means the loose mat and the finished pavement contain the same asphalt, spread to different depths. The order quantity is therefore set by the compacted geometry — the finished thickness on the plans — multiplied by the mix's asphalt density:
Order tons = Area (sq ft) × Compacted thickness (in) ÷ 12 × Density (lb/ft³) ÷ 2,000
Order allowance covers measurement error, edges, cuts, and site losses. It is separate from compaction and is applied exactly once — never stack a compaction factor on top of it.
Why the numbers disagree: two readings of "25 percent"
Search for a loose-to-compacted ratio and you will find 1.15, 1.25 and 1.33 all in circulation for the "same" 25 percent. They are not random — they are two different definitions of what the rolldown factor measures, and picking the wrong one silently shifts every thickness by several percent.
| Convention | Formula | 2 in compacted → loose | Where you see it |
|---|---|---|---|
| A — loose is r% thicker (this site) | loose = compacted × (1 + r) | 2.5 in | Asphalt Paving Handbook §7-5, verbatim |
| B — loose loses r% of its depth | loose = compacted ÷ (1 − r) | 2.67 in | Some calculators and blogs |
Both call the factor "25 percent," but they answer different questions. Convention A asks "how much thicker than the finished depth do I lay it?" and gives 2.5 inches. Convention B asks "what fraction of the loose depth is lost?" and gives 2.67 inches — about 6.7% more material for the same finished lift. The difference is small on a driveway and large across a road program, and it is exactly why two contractors can quote different loose depths from "the same" rolldown.
The rolldown factor by mix, with its source
The rolldown is not a single universal number — it depends mainly on the mix gradation. The Asphalt Paving Handbook gives the two rules of thumb that the industry actually plans against:
| Mix type | Rolldown | 2 in compacted laid loose | Basis |
|---|---|---|---|
| Dense-graded (typical HMA) | ≈25% | 2.5 in | Handbook §7-5 + Figure 109 |
| Gap- / open-graded (SMA, OGFC) | ≈15% | 2.3 in | Handbook §7-5 |
The Handbook states the dense-graded case directly: "assuming a 25-percent rolldown factor on a 2-inch compacted lift thickness, the thickness placed by the paver must be 25 percent thicker or 2.5 inches thick. When gap and open-graded materials are being placed, a rolldown factor of about 15 percent is probably more accurate."
Treat both as planning values, not measured ones. Actual rolldown shifts with lift thickness, mix temperature, aggregate shape, the paver screed setup and the roller type — a vibratory steel drum consolidates differently than a static wheel or a pneumatic. The reliable move is to field-calibrate on the first lift: measure the loose depth behind the screed, roll it, measure the compacted depth, and derive the factor for your crew and your mix.
Converting either direction
With Convention A the two directions are simple inverses. Compacted → loose multiplies by (1 + r); loose → compacted divides by it:
Loose = Compacted × (1 + r ÷ 100) • Compacted = Loose ÷ (1 + r ÷ 100)
- Compacted → loose: a 3-inch compacted spec at 25% is laid at 3 × 1.25 ≈ 3.75 inches loose — set the screed and grade strings to this number.
- Loose → compacted: a 2.5-inch loose mat at 25% rolls down to 2 inches compacted — this is what the inspector measures.
| Compacted | Loose @ ≈25% (dense) | Loose @ ≈15% (gap/open) |
|---|---|---|
| 2 in | 2.5 in | 2.3 in |
| 3 in | 3.75 in | 3.45 in |
| 4 in | 5 in | 4.6 in |
For an interactive conversion with an editable rolldown and the audit steps shown, use the compaction calculator — it runs this same engine in both directions and, by design, produces no tonnage, so there is no way to accidentally fold compaction into the order.
Order by compacted depth, pave by loose depth
The most common practical question — asked constantly on contractor forums — is "do I order asphalt for the compacted depth or the loose depth?" The two depths go to two different places, and mixing them up either short-orders the job or over-orders it:
- Order tons from the COMPACTED depth × the material density. This is the weight that ends up in the finished pavement. A 3-inch spec over your area is what you buy, at about 18.13 net tons per 1,000 sq ft at 145 lb/ft³ — the square feet to tons calculator runs it on your own area, thickness and density.
- Set the paver screed to the LOOSE depth. That is the compacted spec × (1 + rolldown) — about 3.75 inches loose for a 3-inch dense-graded lift. It is a placement dimension for the crew, not a purchase quantity.
- Add exactly one markup: the waste allowance (commonly 5–10%) for edges, cuts, measurement error and site losses. That is the only factor you inflate the order by.
Run the Numbers
- Compaction calculator — convert loose ↔ compacted thickness with an editable rolldown
- Square feet to tons — order tonnage from compacted area, thickness and density
- Coverage calculator — how far a given tonnage spreads at your compacted thickness
- Main asphalt calculator — full estimate with shapes, thickness, allowance and cost
Frequently Asked Questions
How much thicker is loose asphalt than compacted?
By the rolldown factor — about 25% for a typical dense-graded mix and about 15% for gap- or open-graded mixes (Asphalt Paving Handbook §7-5). Under the Handbook's reading a 2-inch compacted lift is laid 2.5 inches loose and a 3-inch lift about 3.75 inches. Field conditions (temperature, lift, roller) move the real number, so calibrate on your first lift.
Do I order asphalt by compacted or loose depth?
By compacted depth. Order tons = compacted volume × material density — about 18.13 net tons for 3 inches over 1,000 sq ft at 145 lb/ft³. The loose depth (about 3.75 inches for that 3-inch lift) is the screed setup number for the crew, not a purchase quantity. Add one waste allowance on top and nothing else.
Does compaction change how many tons I need?
No. Rolling removes air, not material — the loose mat and the compacted pavement contain the same tons at different thicknesses. Running the density on the loose depth instead of the compacted depth over-orders by roughly the rolldown (about 4.53 tons on a 3-in × 1,000 sq ft lift). The only legitimate markup is the one-time waste allowance.
Why do I see 1.15, 1.25 and 1.33 all called a "25%" rolldown?
Two conventions. Convention A — "the loose mat is 25% thicker than compacted" — gives loose = compacted × 1.25 (2 in → 2.5 in); this is the Handbook's verbatim reading and what this site uses. Convention B — "the loose mat loses 25% of its depth" — gives loose = compacted ÷ 0.75 = ×1.333 (2 in → 2.67 in). Same word, ~6.7% different material. Always confirm which one a number is using.
What is the difference between rolldown and waste allowance?
Rolldown is a thickness relationship (loose vs compacted) and never touches the tonnage — it only tells the paver how deep to lay the mat. The waste allowance is a small percentage (typically 5–10%) added once to the order for edges, cuts and site losses. Order allowance covers measurement error, edges, cuts, and site losses. It is separate from compaction and is applied exactly once — never stack a compaction factor on top of it.
Sources & Data Lineage
- Asphalt Paving Handbook, Section 7-5 Layer Thickness — a common rolldown factor for a typical dense-graded mix is approximately 25 percent; about 15 percent for gap- and open-graded materials. Reviewed 2026-09. handbook.asphaltpavement.org
- Asphalt Paving Handbook, Figure 109 — Rule of Thumb Rolldown Factor for Dense-Graded Mixtures. Reviewed 2026-09. handbook.asphaltpavement.org
Planning guidance only — this page does not replace engineering design. Verify quantities and structural requirements with your supplier, contractor and local authority before ordering.