Busbar Ampacity Calculator
Set the width and thickness of a copper busbar and instantly see its cross-section, current carrying capacity, and current density. Pick a foil thickness and the calculator also tells you how many laminations make up that stack - and how the geometry compares against your target current.
1. Set Width & Thickness
2. Operating Assumptions
3. Result
70-95% is a typical design target, leaving margin for ambient and aging.
Tip: the same cross-section can be wide and thin (more flexible, better cooling) or narrow and thick (fits tighter widths, stiffer). Thinner foils make the stack more flexible at the same overall thickness.
Indicative sizing only, based on a simple current-density rule for bare copper at 35-40°C ambient. Actual ampacity depends on temperature-rise limits, enclosure, insulation, duty cycle, and joint design. For a guaranteed rating, request a sized quotation from our engineers.
The Math Behind the Calculator
The calculator applies the standard current-density sizing rule used for first-pass copper busbar design:
Required cross-section S (mm²) = Current I (A) ÷ Current density k (A/mm²)
For a laminated flexible busbar, the cross-section is simply width × foil thickness × number of laminations. Example: a 30 A connection at a conservative 1.8 A/mm² needs about 17 mm² - achievable as a 20 mm wide busbar with four 0.2 mm foils (16 mm², slightly under) or five foils (20 mm², comfortable).
The same section can be built many ways: more thin foils give a more flexible busbar, fewer thick foils a stiffer one. Pick the combination that fits your space and movement requirement, then read the full sizing & ampacity guide for temperature rise and derating factors.
Calculator FAQ
How does this busbar calculator work?
You set the busbar width and overall thickness; the calculator computes the copper cross-section (width × thickness) and multiplies it by a current density appropriate to your installation (1.5-2.5 A/mm² covers most cases) to give the current carrying capacity. Choosing a foil thickness also shows how many laminations build up that stack. Enter a target current to see utilization and the actual current density at that load.
What current density should I use?
Use 1.5 A/mm² for insulated busbars in enclosed panels, 1.8 A/mm² for bare copper in typical enclosed switchgear, 2.2 A/mm² with good ventilation, and up to 2.5 A/mm² for short busbars in free air. When in doubt, choose the lower value - the result is a cooler-running, longer-lived busbar.
Can I use this calculator in reverse - from dimensions to current?
Yes. Set the width, foil thickness, and lamination count of an existing busbar, and the "Carries approximately" result shows its indicative continuous ampacity at the chosen current density - regardless of what target current you entered.
Is the result a guaranteed rating?
No - it is a first-pass engineering estimate. Real ampacity depends on permissible temperature rise, ambient temperature, enclosure ventilation, insulation, duty cycle, and joint quality. SVS Maverick verifies every busbar design against the actual operating conditions before quoting; send us your result for a confirmed recommendation.
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Found Your Cross-Section?
Send us the result along with your terminal dimensions and operating conditions. Our engineers will verify the sizing against actual temperature rise and quote a custom flexible busbar - manufactured in Bangalore, India and supplied worldwide.
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