Calculation methodology

General rules

• Calculations run in the browser. Entered values are kept only in the page address, so the result survives a refresh and can be shared as a link.
• Decimal separator: comma in the Polish version, point in the English version. Fields accept both.
• A result appears only when the required data are complete – the missing fields are listed instead. The calculator never shows 0 in place of a missing value.
• Calculations use unrounded values; rounding (half up) applies to display only.
• In the chemical composition tools, elements not entered (other than the required ones) are taken as 0% and the result is marked as based on incomplete data, listing those elements. An entered 0 counts as a given value. The sum of elements must not exceed 100%.
• Unusual values (e.g. welding current above 1500 A or C above 2.5%) do not block the calculation but are flagged next to the field and above the result – usually a typo or a misplaced decimal point. Warning ranges are indicative.
• A link to a calculation contains all parameters of the current mode, so it reproduces the result even if the example values change. Example values are labelled “Example” in the result until the first change.
• Saved variants and the list of recently used tools are stored only in this browser.
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Arc energy and heat input

Arc energy E and heat input Q from welding current, arc voltage and travel speed.

Formulas

E = U · I / v · 10⁻³  [kJ/mm], v in mm/s

Q = k · E

1 kJ/mm = 10 kJ/cm

Calculation rules

• Thermal efficiency factor k per ISO/TR 17671-1 (EN 1011-1): MMA (111) 0.8 · SAW (121) 1.0 · MIG/MAG (131, 135, 136, 138) 0.8 · TIG (141) 0.6.
• Speed: mm/min ÷ 60, m/min × 1000 ÷ 60 → mm/s. Changing the unit does not convert the entered number – check that the number matches the selected unit.
• In range mode min must not be greater than max – otherwise no result is shown and the fields are marked.
• Min–max range: minimum from I min, U min and v max; maximum from I max, U max and v min; mean = (min + max) / 2.
• ±25% band (× 0.75 / 1.25): heat input range of qualification per ISO 15614-1 (level 2 – upper limit where impact requirements apply, lower limit where hardness requirements apply).
• ±15% band (× 0.85 / 1.15): permitted deviation for aluminium alloys of group 23 per ISO/TR 15608 (precipitation-hardenable alloys) according to EN ISO 15614-2:2025.
• Tolerance check: deviation = (Q − Q₀) / Q₀ · 100%; ±15% and ±25% limits inclusive. Check detailed requirements in the standard for your material and in the WPQR.

Rounding

kJ/mm – 3 decimal places, kJ/cm – 2 decimal places, deviation in % – 1 decimal place.

Carbon equivalents

Carbon equivalents CE, PCM, CET and CEN from the steel chemical composition in wt%.

Formulas

CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

PCM = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B

CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40

CEN = C + A(C) · [Si/24 + Mn/6 + Cu/15 + Ni/20 + (Cr + Mo + Nb + V)/5 + 5B]

A(C) = 0.75 + 0.25 · tanh[20 · (C − 0.12)]

Calculation rules

• Weldability rating by CE (indicative scale – not defined by a standard; preheat is determined e.g. per EN 1011-2): ≤ 0.35 excellent · ≤ 0.40 very good · ≤ 0.45 good · ≤ 0.50 moderate · above 0.50 poor.
• Carbon content C is required. Other elements left empty are taken as 0% – the calculator lists which elements were not entered.
• Min–max range: CE for the minimum and maximum composition, the difference Δ and the weldability rating for both limits. For each element min ≤ max; other pairs are entered completely or not at all.
• CEN is calculated with the Yurioka formula including the A(C) function.

Rounding

3 decimal places.

Schaeffler diagram

Chromium and nickel equivalents and the position of the composition on a simplified Schaeffler diagram.

Formulas

Cr_eq = Cr + Mo + 1.5 · Si + 0.5 · Nb

Ni_eq = Ni + 30 · C + 0.5 · Mn

Calculation rules

• Cr and Ni contents are required. Other elements left empty are taken as 0% (with a notice).
• Simplified diagram: four boundary lines divide the field Cr_eq 0–40%, Ni_eq 0–30% into seven regions: A, A + M, M, A + F, A + F + M, F + M, F.
• The result shows the region where the point lies. It does not give the ferrite content (%) or ferrite number and does not account for nitrogen or cooling conditions; treat points close to boundary lines as indicative.
• A point outside the diagram field is marked with an arrow on the edge and the result has the status “Outside the diagram”; the region name at the edge is then indicative only.
• The calculator gives the distance from the point to the nearest boundary line of its region (in % on the diagram axes). Below 1% a warning says the classification is uncertain.

Rounding

2 decimal places.

PREN – pitting resistance

Pitting resistance equivalent number of stainless steels from the chemical composition in wt%.

Formulas

PREN = Cr + 3.3 · (Mo + 0.5 · W) + 16 · N

Calculation rules

• Cr content is required. Mo, W and N left empty are taken as 0% (with a notice).
• Contributions: Cr, 3.3 · Mo, 1.65 · W, 16 · N.

Rounding

PREN – 1 decimal place, contributions – 2 decimal places.

Fillet weld size

Convert fillet weld throat thickness a to leg length z and back.

Formulas

z = a · √2

a = z · √2 / 2

Calculation rules

• Equal-leg fillet weld with a right-angled triangular cross-section (90° between the parts).
• Quick-reference table for values from 2 to 13 mm.

Rounding

2 decimal places.

Intermittent weld segments

Intermittent welds: gap length, total length, drawing designation and clash with an obstacle.

Formulas

e = (L − n · l) / (n − 1)

L = n · l + (n − 1) · e

Designation: n × l (e)

Calculation rules

• Gap length needs at least 2 welds; when n · l > L, the welds do not fit in the length.
• Weld Si occupies [(i − 1) · (l + e); (i − 1) · (l + e) + l] from the start.
• Clash: a weld overlaps the obstacle when it starts before the obstacle ends and ends after the obstacle starts (touching is not a clash).

Rounding

Lengths – 1 decimal place.

Flowmeter reading correction

Actual shielding gas flow when the flowmeter is scaled for a different gas.

Formulas

without viscosity: Q = Q₀ · √(ρ_cal / ρ_act)

with viscosity: Q = Q₀ · √(ρ_cal · η_act / (ρ_act · η_cal))

Calculation rules

• Q₀ – flowmeter reading, ρ – density [kg/m³], η – dynamic viscosity [µPa·s]; “cal” – the gas the flowmeter is scaled for, “act” – the actual gas.
• Gas density and viscosity as listed in the calculator table: density at 0 °C and 1013 hPa, viscosity at about 20 °C; for mixtures, density is the composition-weighted mean and viscosity follows Wilke’s rule.
• The viscosity variant is an approximate model (labelled in the calculator). Results are indicative; for exact settings use the flowmeter manufacturer’s tables.

Rounding

Flow – 2 decimal places, factor – 4 decimal places, difference in % – 1 decimal place.