What size wood chipper do I need?
The answer depends on your largest branches, wood type, and power source. Enter those three things below — the calculator returns the minimum and comfortable HP, then matches chippers from our reviews that fit your spec.
How big of a wood chipper do you actually need?
Pruning, storm cleanup, shrub and small tree branches up to 4 inches. A 15–25 HP PTO chipper or a standalone gas chipper in the 6–14 HP range handles the typical suburban or rural homeowner load.
Hedgerow clearing, orchard pruning, woodlot thinning with branches up to 6–8 inches. You need a PTO chipper matched to a 30–50 HP tractor, or a purpose-built commercial gas unit.
Whole-tree chipping, large hardwood trunks, sustained daily use. This range typically means a tow-behind drum chipper on a 50+ HP tractor or a truck-mount unit from Bandit, Vermeer, or Morbark.
Woodchipper HP calculator
Tell us what you’ll chip. We’ll calculate the minimum and comfortable HP, then match woodchippers from our reviews that fit your spec.
Reading: A 6-inch hardwood chipper needs 35 pto hp for comfortable sustained chipping. Tractor PTO HP is typically 10–15% lower than rated engine HP.
The math behind the calculator
The base formula: PTO HP ≈ 3.5 × branch diameter (in) × wood multiplier. Gas engine chippers use 2.8 HP/inch because direct drive avoids drivetrain losses. Wood multipliers: softwood 0.78×, mixed 1.0×, hardwood 1.25×.
The “comfortable” HP is the minimum × 1.35 — the working range where feed rate stays consistent and the flywheel doesn’t bog on knots or hardwood. This matches manufacturer-recommended HP ranges within a few percent for all the chippers in our database.
Matched product recommendations filter our 19 reviewed models by: (1) correct power type, (2) maxBranchIn ≥ your requested size, (3) HP min ≤ comfortable HP + 5. Results are sorted by closest capacity match, then price.
Complete PTO HP sizing chart (by branch diameter)
| Max branch | Softwood — min / comfortable pto hp | Mixed — min / comfortable pto hp | Hardwood — min / comfortable pto hp |
|---|---|---|---|
| 3″ | 8 / 11 HP | 11 / 14 HP | 13 / 18 HP |
| 4″ | 11 / 15 HP | 14 / 19 HP | 18 / 24 HP |
| 5″ | 14 / 18 HP | 18 / 24 HP | 22 / 30 HP |
| 6″ | 16 / 22 HP | 21 / 28 HP | 26 / 35 HP |
| 7″ | 19 / 26 HP | 25 / 33 HP | 31 / 41 HP |
| 8″ | 22 / 29 HP | 28 / 38 HP | 35 / 47 HP |
| 9″ | 25 / 33 HP | 32 / 43 HP | 39 / 53 HP |
Values are tractor PTO HP after drivetrain losses. Rated engine HP is typically 10–15% higher — a 35 HP engine tractor produces roughly 30 PTO HP.
Complete gas engine HP sizing chart (by branch diameter)
| Max branch | Softwood — min / comfortable engine hp | Mixed — min / comfortable engine hp | Hardwood — min / comfortable engine hp |
|---|---|---|---|
| 3″ | 7 / 9 HP | 8 / 11 HP | 10 / 14 HP |
| 4″ | 9 / 12 HP | 11 / 15 HP | 14 / 19 HP |
| 5″ | 11 / 15 HP | 14 / 19 HP | 18 / 24 HP |
| 6″ | 13 / 18 HP | 17 / 23 HP | 21 / 28 HP |
| 7″ | 15 / 21 HP | 20 / 26 HP | 24 / 33 HP |
| 8″ | 17 / 24 HP | 22 / 30 HP | 28 / 38 HP |
| 9″ | 20 / 27 HP | 25 / 34 HP | 32 / 43 HP |
Values are rated engine HP on the chipper itself. Honda GX commercial engines deliver closer to rated HP than generic engines under load.
Frequently asked questions
- What size wood chipper do I need?
- Size your chipper to your 80th-percentile branch — the largest branch you'll regularly chip, not the absolute biggest you'll ever encounter. A 6-inch chipper handles most homeowner and small-farm work. Step up to an 8-inch model if you're regularly processing hardwood limbs from mature trees. The calculator above will give you the exact HP range once you enter your branch diameter and wood type.
- What can a 6-inch wood chipper handle?
- A 6-inch chipper processes branches up to 6 inches in diameter. That covers most pruning and storm-cleanup work on mature trees — apple, oak, and maple limbs up to about wrist-to-forearm thickness. For softwood (pine, spruce, cedar) a 6-inch chipper is straightforward; for dense hardwood like hickory or locust, you'll want to be at the comfortable-HP end of the range, not the minimum.
- How big of a wood chipper do I need for my tractor?
- Match chipper capacity to your tractor's PTO HP, not the other way around. A 40-HP tractor can comfortably run a 6-inch PTO chipper; a 60-HP tractor can handle an 8-inch chipper. The rule of thumb is 3.5 PTO HP per inch of max branch diameter for hardwood — so a 6-inch chipper needs 21 HP minimum and about 28 HP to run comfortably. Use the calculator above with your branch size to get the exact number for your wood type.
- Is this HP calculator accurate?
- The formula matches manufacturer recommended-range tables within ±2 HP across 4–9 inch chipper sizes. It's most accurate for seasoned hardwood at full capacity (the default assumption). Green wood and softwood need 20–30% less HP — the calculator's softwood multiplier accounts for this.
- Engine HP vs PTO HP — which number should I enter?
- Select 'PTO tractor' if you're running a tractor chipper, and we'll size to PTO HP. Tractors lose 10–15% between engine and PTO, so a 35 HP engine tractor produces ~30 PTO HP. The calculator handles this distinction automatically.
- Does the calculator account for hydraulic feed draw?
- Partially — the comfortable-HP padding (35% above minimum) covers typical hydraulic pump draw of 2–4 HP. For commercial-grade hydraulic-feed chippers pushing hardwood, size up one tier above the comfortable number.
- Can I use this for commercial chippers (12+ inch)?
- The calculator covers 3–9 inch chippers, which is where homeowner and small-commercial buyers live. For 12+ inch commercial tow-behind chippers (Bandit, Vermeer, Morbark), work with your dealer — those machines often run on optimized engine-clutch-flywheel combinations that don't fit a generic formula.
- What chippers does the calculator match against?
- Our full review database: 7 Woodmaxx PTO chippers (MX-8500G+ through MX-9900), 3 Woodland Mills PTO chippers (WC46/WC68/WC88), 6 MechMaxx gas chippers (GS650 through CROBA TX1000), and 1 MechMaxx PTO unit (BX42S). Results link to full reviews with specs and affiliate price checks.