Engineering calculator reviewed for preliminary design use · Last updated: March 2026
EngiCompute calculators are screening-level estimation tools, not formal code-compliance software. They apply recognized equations and standards (Darcy-Weisbach, ASME VIII, B31.3, API 520) to give fast, defensible preliminary numbers. This page explains the estimation philosophy and how to interpret results responsibly before detailed design.
This page makes clear what each EngiCompute calculator does — and does not — compute, so you can interpret results responsibly in practice.
EngiCompute calculators are screening-level (preliminary) estimation tools. They are not formal code-compliance software, and they do not replace certified design calculation reports.
Their purpose is to quickly confirm whether a number is in the right order of magnitude and within a reasonable range, so you can decide whether to proceed to detailed design. They suit sizing during FEED and basic design, sanity checks during design reviews, early evaluation at the estimation stage, and cross-checking vendor responses.
In real engineering work there are many points where you need to confirm that the direction is right before committing to detailed calculation. Getting a first cut at a pipe diameter, estimating the head a pump must deliver, understanding the order of magnitude of a vessel wall — these judgments are made before any full code calculation is run.
Estimation tools support these early decisions in seconds. Their greatest value is preventing the rework that comes from carrying a wrong assumption deep into detailed design.
Each calculator is based on published literature and recognized industry equations and standards:
• Fluid mechanics: Darcy-Weisbach, Ergun (packed beds), Joukowski (water hammer), Bernoulli • Pressure vessels: ASME Section VIII Division 1 • Piping: ASME B31.3 Process Piping • Flanges: ASME B16.5 • Relief valves: API 520 / API 521 • Flow meters: ISO 5167 (orifice) • Control valves: ISA/IEC standards (Cv/Kv) • Heat exchangers: LMTD method, Q = U·A·ΔTlm
The equation used, assumptions, and applicable range are stated on each calculator page.
Estimation tools solve only the key governing equation under typical assumptions (steady-state, single-phase, ideal gas, no corrosion allowance, no external loads, etc.). Formal design must additionally account for:
• Project-specific design conditions and margins • Minor losses, fittings, and internals • Corrosion allowance, mill tolerance, and fabrication tolerances • Detailed code provisions (reinforcement, external pressure, cyclic loads) • Verification against vendor and as-built data
For this reason, do not adopt the results on this site as final design values.
• Treat every result as an estimate and apply an appropriate design margin • Always confirm the flow regime (Reynolds number) and the applicable range • A minimum wall thickness is not a procurement thickness — add corrosion allowance and tolerance, then round up to a commercial gauge • Geometric volume is not working volume • Have critical design decisions verified by a qualified engineer or engineering firm
See the "Worked Example" and "Common Mistakes & Misuse" sections on each calculator page as well.
For preliminary estimation and educational use only. Results may depend strongly on assumptions, input data, fluid or material properties, and the range of validity of the underlying equation. Verify critical calculations independently and follow the applicable code, specification, and formal engineering review process before using any result for design, procurement, fabrication, operation, or safety decisions.