Methodology

Methodology & Accuracy

How our calculators work, what they assume, and where theoretical results stop.

Accuracy notice

These calculators are reference tools. They give theoretical values from standard formulas and do not replace manufacturer specifications, applicable standards, qualified engineering analysis or proper safety procedures. We do not publish component pressure ratings or other safety-critical specifications.

Cylinder formulas

Piston area: A_piston = π × bore² ÷ 4
Rod area: A_rod = π × rod² ÷ 4
Annular area: A_annular = A_piston − A_rod
Extend force: F_extend = pressure × A_piston
Retract force: F_retract = pressure × A_annular
Extend speed: V_extend = Q ÷ A_piston
Retract speed: V_retract = Q ÷ A_annular
Stroke time: T = stroke ÷ V
Cycle time: T_cycle = T_extend + T_retract
Chamber volume: V = effective area × stroke
Hydraulic power (Imperial): HP = PSI × GPM ÷ 1,714
Hydraulic power (metric): kW = bar × L/min ÷ 600

Q is the supplied flow converted to volume per second in the same length units as the area. Metric force uses bar × 0.1 = N/mm², so N/mm² × mm² = N.

Unit conversions

1 US gallon: 231 in³ (exact)
GPM → in³/s: × 231 ÷ 60
lbf → US short tons-force: ÷ 2,000
1 inch: 25.4 mm (exact)
1 bar: 14.5038 PSI = 0.1 N/mm²
1 US gallon: 3.785411784 L
L/min → mm³/s: × 1,000,000 ÷ 60
mm³ → L: ÷ 1,000,000
N → tonnes-force: ÷ (1,000 × 9.80665)

What “theoretical” means

Theoretical results assume full pressure acts on the piston, all supplied flow reaches the cylinder, and there are no losses. Real force and speed can be lower because of pressure drop, back pressure, seal friction, internal leakage, component efficiency, temperature, wear and other system conditions.

Rounding

Calculations use full precision internally. Displayed results are rounded to a practical number of digits (for example, forces to the nearest pound-force or newton). Values shown in “Show the Math” are rounded for readability, so re-doing a step by hand with the rounded numbers may differ in the last digit.