Enter the alloy resistivity, strip thickness and width to get sheet resistance (Ω/□), plus the length needed for a target resistance. Works for resistance ribbon, foil and any thin conductive strip.
| Quantity | Formula |
|---|---|
| Quantity | Formula |
| Sheet resistance | Rs (Ω/□) = ρ (μΩ·m) ÷ t (mm) ÷ 1000 |
| Resistance of a strip | R (Ω) = ρ (μΩ·m) × L (m) ÷ [ w (mm) × t (mm) ] |
| Number of squares | N = L (mm) ÷ w (mm) → R = Rs × N |
| Length for target R | L (mm) = R × w (mm) ÷ Rs |
| Sheet resistance Rs | Resistance R | |
|---|---|---|
| Sheet resistance Rs | Resistance R | |
| Unit | Ω/□ (ohm per square) | Ω |
| Depends on | Resistivity and thickness only | Resistivity, thickness, length and width |
| Changes with size? | No — size independent | Yes — longer and narrower means more resistance |
| Typical use | Comparing foil / ribbon of different thickness | Sizing an actual element |
| Alloy | Family | ρ (μΩ·m) | Max temp. |
|---|---|---|---|
| Alloy | Family | ρ (μΩ·m) | Max service temp. (°C) |
| 0Cr25Al5 | FeCrAl | 1.40 | 1300 |
| 0Cr21Al6Nb | FeCrAl (Nb) | 1.45 | 1350 |
| 0Cr27Al7Mo2 | FeCrAl (Mo) | 1.53 | 1400 |
| 1Cr13Al4 | FeCrAl (low Cr) | 1.25 | 950 |
| Cr20Ni80 | Ni-Cr | 1.09 | 1200 |
| Cr30Ni70 | Ni-Cr | 1.18 | 1250 |
| Cr15Ni60 | Ni-Cr-Fe | 1.12 | 1150 |
| Cr20Ni35 | Ni-Cr-Fe | 1.04 | 1050 |
| Constantan 6J40 | Cu-Ni | 0.49 | 400 |
| Manganin 6J12 | Cu-Mn-Ni | 0.45 | — |
| Pure nickel Ni200 | Ni | 0.096 | 600 |
What is sheet resistance?
Sheet resistance (Rs, measured in Ω/sq or Ω/□) is the resistance of a square sheet of material, independent of the square size. For a thin strip or foil it equals resistivity divided by thickness: Rs = ρ / t. Because it is per-square, the same value applies whether the square is 1 mm or 1 m on a side.
What is the formula for sheet resistance?
Rs (Ω/□) = ρ (μΩ·m) ÷ t (mm) ÷ 1000. Example: 0Cr25Al5 with ρ = 1.40 μΩ·m at 1.0 mm thickness gives Rs = 1.40 / 1.0 / 1000 = 0.0014 Ω/□.
How do I get resistance from sheet resistance?
R (Ω) = Rs × L (mm) ÷ w (mm), where L is the current-path length and w is the width. For a strip, the number of squares is simply length divided by width.
Why does changing thickness change power?
Thickness changes both resistance and cross-sectional area, so at a fixed voltage the power changes. Halving the thickness roughly doubles the resistance and therefore roughly halves the power at constant voltage. Always recalculate after a thickness change.
Which alloys are used for resistance ribbon?
FeCrAl grades (0Cr25Al5, 0Cr21Al6Nb, 0Cr27Al7Mo2) for high-temperature heating elements; Ni-Cr grades (Cr20Ni80, Cr15Ni60, Cr30Ni70, Cr20Ni35) where ductility and thermal-fatigue resistance matter; Cu-Ni/Mn-Ni precision grades (Constantan 6J40, Manganin 6J12/6J13) for precision shunts and sampling resistors.
Shanghai Xinxiang Alloy Materials Co., Ltd. (founded 2014) is a source manufacturer of electric heating alloys and nickel-based precision alloys, with an approximately 20,000 m² production base in Taixing, Jiangsu, 48+ pieces of melting / forging / rolling / drawing / heat-treatment / testing equipment, 200+ staff and about 7,500 t annual capacity.
We supply FeCrAl and Ni-Cr resistance ribbon and wire, pure nickel wire and strip (Ni200 / Ni201 / N4 / N6), precision resistance alloys (Constantan / Manganin), thermocouple materials and heat-resistant steel furnace parts. Wire φ0.03–10 mm; strip 0.05–3.5 mm × 2–300 mm.
Contact: +86 136 6174 5686 / +86 21 6911 6339 · Contact page
Resistivity values are typical at 20 °C and compiled from GB/T 1234, ASTM B344, DIN 17470/17471 and published manufacturer data sheets. Always verify against the mill certificate before finalising a design.
