How big is a dumpy bag of logs?

If you heat with wood in the UK, you’ve probably seen logs sold in a ‘dumpy bag’, ‘bulk bag’ or even a ‘ton bag’. The snag? Those names aren’t standardised. This guide explains exactly how big a dumpy bag of logs is, how much usable firewood you actually get, and how it compares with other ways to buy logs – so you can order the right amount first time.

Quick answer

Typical empty bag size (UK):

80 × 80 × 80 cm (0.51 m³ if filled to the brim)
85 × 85 × 85 cm (0.61 m³ brim-full)
90 × 90 × 90 cm (0.73 m³ brim-full)

What you usually receive (loose-filled logs):

Because logs are irregular and bags aren’t packed like a crate, a “90×90×90 cm” dumpy bag typically contains ~0.55–0.65 m³ of loose logs. Smaller bags scale accordingly.

Rule of thumb:

1 dumpy bag (90 cm) ≈ 0.6 m³ loose
~2 dumpy bags ≈ 1.2 m³ loose (about 0.75–0.85 m³ stacked)

Important: A “ton bag” is a builders’ nickname for the bag style—not a promise of weight. Weight varies hugely by wood species, moisture content and log length.

Why “bag size” and “log volume” aren’t identical

A dumpy bag is defined by its external dimensions, but firewood volume is about the space the loose logs actually occupy inside. Three factors explain the gap:

Loose vs stacked: Loose logs trap air gaps. A loose cubic metre usually equals ~0.6–0.7 m³ stacked.
Log length & split size: Shorter, chunkier logs create more voids than longer, slender splits.
Fill level & bag stance: Most bags are loose-filled below the rim; sling points and bulging sides also change internal capacity.

Common UK dumpy/bulk bag sizes and what they mean

Bag label (common UK)	External size (cm)	Brim-full geometric volume	Typical loose logs supplied	Approx stacked equivalent*
Small bulk bag	80 × 80 × 80	0.51 m³	~0.40–0.50 m³	~0.25–0.35 m³
Standard bulk/dumpy	85 × 85 × 85	0.61 m³	~0.50–0.60 m³	~0.30–0.40 m³
Large bulk/dumpy	90 × 90 × 90	0.73 m³	~0.55–0.65 m³	~0.35–0.45 m³

*Using the common conversion that 1.0 m³ loose ≈ 0.6–0.7 m³ stacked. These are practical ranges, not lab measurements.

How many dumpy bags equal 1 cubic metre of logs?

It depends whether you mean loose or stacked volume.

To get ~1.0 m³ of loose logs:
If one large dumpy bag ≈ 0.6 m³ loose, you’ll need ~1.7 bags. In practice: 2 bags.
To get ~1.0 m³ stacked:
You’ll typically need ~1.4–1.7 m³ loose, which is ~2–3 dumpy bags, depending on log length and how neatly you stack.

“Ton bag” myth—how much does a dumpy bag weigh?

There is no fixed weight. Weight varies by:

Species: Hardwood (e.g., oak, ash, birch) is heavier than softwood (e.g., spruce, pine).
Moisture: Kiln-dried (≤20% moisture) is far lighter—and burns better—than wet or “green” logs.
Length & density: Short, dense hardwood pieces weigh more per bag than long, open-grained softwood pieces.

Expect a very wide range: the same bag size can differ by well over 100 kg depending on species and moisture. Always buy by stated volume and moisture, not weight.

Kiln-dried vs seasoned: why volume is only half the story

UK “Ready to Burn” standards require domestic firewood sold in small volumes to be ≤20% moisture content, because drier logs:

Ignite faster and produce more heat per log
Reduce soot and tar build-up in your flue and on stove glass
Burn cleaner, lowering smoke and particulates

If you compare two identical dumpy bags—one kiln-dried hardwood, one poorly seasoned hardwood—the kiln-dried bag will deliver far more usable heat, even if they look similar in volume.

Dumpy bag vs crate vs loose-tipped: what gives best value?

Dumpy/bulk bag (loose-filled):
Convenient to move and store; good for mixed/regular usage. Volume has air voids and varies a little by fill method.
Crate (stacked):
Logs are tightly stacked in a wooden crate. You see exactly what you’re getting, with less void space. If you want maximum usable wood per cubic metre, crates are often the most volume-efficient option.
Loose-tipped delivery:
Usually the lowest handling cost per m³ loose. Needs driveway access and space to stack after delivery.

How many logs are in a dumpy bag?

It depends on log length (commonly 25 cm in the UK), split size and species. As a very rough guide:

Large dumpy (≈0.6 m³ loose, 25 cm logs):
~200–300 pieces (mixed split sizes)
Standard dumpy (≈0.5 m³ loose):
~170–250 pieces

Treat these as ranges, not guarantees.

Will one dumpy bag heat my home for winter?

Usage varies widely with:

Stove efficiency and output (kW)
Home insulation and room size
Burn habits (evening top-ups vs all-day fires)
Wood species and moisture

A typical UK wood-burner user might burn anywhere from 1 to 4+ cubic metres (loose) across a heating season. For occasional evening burns, one or two large dumpy bags may suffice; for regular heating, plan on more—or consider a crate for better density and value.

How to compare offers fairly (and avoid surprises)

Ask for stated loose or stacked volume (in m³), not just “bag size”.
Check moisture content (aim for ≤20%, “Ready to Burn”).
Confirm log length (e.g., 25 cm fits most UK stoves).
Clarify species (birch lights quickly; ash/oak burn longer).
Delivery method & access (sack barrow, tail-lift, crate footprint).
Sustainability (sourcing & any tree-planting contributions).

Worked examples (so you can plan your order)

I want ~1 m³ of loose logs: Order 2 large dumpy bags (you’ll have ~1.1–1.3 m³ loose).
I want ~1 m³ stacked neatly in my log store: Order ~2–3 dumpy bags (depending on bag size and how tightly you stack), or choose a 1 m³ stacked crate for precision.
I burn most evenings for 3 winter months: Many households use ~1.5–2.5 m³ loose: typically 3–4 large dumpy bags or a crate plus a bag. Adjust for your stove and space.

FAQs:

Is a dumpy bag the same as a bulk bag? Yes—UK sellers use both terms for the same woven PP builders’ bag.

Is a “ton bag” a tonne of logs? – No. It’s just a nickname for the bag style. Always buy by volume and moisture content.

What log length should I choose? – 25 cm suits most UK stoves. If your firebox is small or unusually shaped, measure first.

Hardwood or softwood? – Kiln-dried hardwood (e.g., ash, oak and birch) generally gives longer, hotter burns. Softwood lights fast and is great as kindling or for shoulder seasons.

Can I store a dumpy bag outside? – Yes, if it’s off the ground, covered on top only (sides open for airflow), and sheltered from constant rain. Transfer to a log store for best results.

Explore kiln-dried bulk bags from FirewoodFund

Now that you know exactly how big a dumpy bag of logs is, you can confidently choose the right amount of firewood for your home. At FirewoodFund.co.uk, we supply premium kiln-dried hardwood logs in bulk bags—all Ready to Burn certified.

Every order contributes to tree planting across the UK, and you can even book your preferred delivery date at checkout.

Explore our full range of kiln dried log bulk bags today and enjoy a cleaner, hotter, and more efficient burn:-