What size hydraulic cylinder do I need for a 20-ton log splitter?

At a standard 3,000 PSI relief pressure, a 4.0-inch bore cylinder outputs 18.85 tons. To achieve a true 20-to-22-ton split rating, a 4.5-inch bore cylinder is required, generating 23.85 tons.

What size pump and engine do I need for a 4-inch cylinder?

A 4-inch bore cylinder with a 24-inch stroke holds 1.31 gallons. To extend in 9 seconds, you need at least a 13 GPM or 16 GPM 2-stage hydraulic pump paired with a 6.5 HP to 8.5 HP gas engine.

DIY Hydraulic Cylinder Force, Pump GPM & Cycle Speed Sizer

1. Enter Build Requirements

Target Pressing Force (Tons): Standard log splitters: 20–28 tons. Shop presses: 12–50 tons.

System Operating Pressure (PSI): Continuous relief valve setting on directional control valve.

Cylinder Stroke Length (Inches):

Desired Extension Time (Seconds): Time required for ram to extend fully under no-load rapid flow.

Cylinder Mount Configuration:

2. Hydraulic Engineering Specs

Recommended Standard Cylinder Bore:

4.0" Bore × 24" Stroke

Actual Output Force: 18.8 Tons @ 3,000 PSI

Required Pump Delivery Flow (GPM):

16 GPM (2-Stage Hi-Lo)

Extension: 9.0s | Retraction: 6.8s (w/ 1.75" Rod)

Fluid Displacement Per Extension Stroke:

1.31 Gallons

Minimum hydraulic oil reservoir size: ~5.0–6.5 Gallons.

Minimum Gas Engine Horsepower (Shaft HP):

8.5 HP (Gas Engine)

Based on 2-stage unloader kick-down @ 650 PSI transition.

Standard Cylinder Bore Force & Cycle Time Reference (at 3,000 PSI)

Standardized thrust capacities, displacement volumes, and 2-stage pump pairings across common cylinder bores:

Bore Diameter	Piston Area	Force @ 2,500 PSI	Force @ 3,000 PSI	Fluid Vol (24" Stroke)	Recommended 2-Stage Pump	Min Engine HP
3.5 Inch	9.62 sq. in.	12.0 Tons	14.4 Tons	1.00 Gallons	11 GPM (Hi-Lo)	5.5–6.5 HP
4.0 Inch	12.57 sq. in.	15.7 Tons	18.8 Tons	1.31 Gallons	13–16 GPM (Hi-Lo)	6.5–8.5 HP
4.5 Inch	15.90 sq. in.	19.9 Tons	23.9 Tons	1.65 Gallons	16 GPM (Hi-Lo)	8.5–9.5 HP
5.0 Inch	19.63 sq. in.	24.5 Tons	29.4 Tons	2.04 Gallons	22 GPM (Hi-Lo)	13.0 HP+

Frequently Asked Questions

How do you calculate hydraulic cylinder tonnage?

Multiply piston area (sq in) by pressure (PSI) and divide by 2,000 lbs. A 4" bore cylinder has an area of 12.57 sq in, generating 37,710 lbs of force at 3,000 PSI (18.85 tons).

Why is a 2-stage pump preferred over a single-stage pump?

A 2-stage pump delivers rapid high flow at low pressure (<650 PSI) for fast ram advance, then automatically kicks down to low flow at 3,000 PSI for splitting knots, allowing smaller 6.5–9 HP engines to run the system.

Verified Hydraulic System Components

Hydraulic Ram

Welded Hydraulic Cylinder

Heavy-duty welded cylinder sized to match your calculated bore, stroke, and continuous pressure rating.

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Power Unit

2-Stage Hydraulic Gear Pump

Hi-Lo rapid-advance gear pump delivering rapid cycle times with high-pressure kick-down when splitting knots.

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Flow Control

Auto-Return Detent Valve

Heavy-duty directional control valve with hands-free pressure-release detent and built-in relief valve.

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Fluid Dynamics & Safety Disclaimer: High-pressure hydraulic circuits operate under hazardous energy. Calculations are theoretical estimations. Verify pressure ratings on all fittings, hoses, and valves before operation.