Electronics
Transformer Turns Ratio Calculator
Enter the primary voltage plus the primary and secondary turns counts to find the secondary voltage, secondary current, and whether the transformer steps up or down.
Find secondary voltage and current from an ideal transformer's turns ratio.
Assumes an ideal (lossless) transformer. Real transformers run a few percent lower on output voltage due to winding resistance and core losses.
Ideal transformer relationship
Vp/Vs = Np/Ns = Is/Ip
Voltage scales directly with the turns ratio, while current scales inversely — a step-down transformer that halves voltage doubles available current, assuming no losses.
How to use
- Enter the primary (input side) voltage and its winding turns count.
- Enter the secondary (output side) turns count.
- Optionally enter primary current to see the corresponding secondary current an ideal transformer would deliver.
Example
Input: Vp = 120V, Np = 1000 turns, Ns = 100 turns, Ip = 1A
Output: Vs = 12V, Is = 10A, ratio 10:1, step-down
Student-friendly breakdown
This walkthrough emphasizes the most searched ideas for Transformer Turns Ratio Calculator: transformer ratio calculator, turns ratio calculator, transformer voltage calculator. Start with the formula above, then follow the guided steps to double-check your work. For quick revision, highlight the givens, plug into the equation, and finish by verifying your units.
Need more support? Use the links below to open the long-form guide, browse additional examples, or hop into adjacent calculators within the same topic — each one is a quick way to double-check your work or handle a related question without starting from scratch.
Deep dive & study plan
Transformer Turns Ratio Calculator: Finds secondary voltage and current from a transformer's turns ratio. It's built around transformer ratio calculator, turns ratio calculator, transformer voltage calculator, so you can go from a raw question to a checked answer without switching tools.
The math behind it: Voltage scales directly with the turns ratio, while current scales inversely — a step-down transformer that halves voltage doubles available current, assuming no losses. The core relationship is Vp/Vs = Np/Ns = Is/Ip, shown above the calculator so you can see exactly how your inputs turn into the result.
To use it well: (1) Enter the primary (input side) voltage and its winding turns count. (2) Enter the secondary (output side) turns count. (3) Optionally enter primary current to see the corresponding secondary current an ideal transformer would deliver. Keep your units consistent as you go, and re-run a case you already know the answer to — it's the fastest way to catch a typo before it throws off a result you're relying on.
Worked example: entering Vp = 120V, Np = 1000 turns, Ns = 100 turns, Ip = 1A returns Vs = 12V, Is = 10A, ratio 10:1, step-down. Try swapping in your own numbers next, especially a case you're unsure about, before you use this for something that matters.
Quick retention checklist
- Speak the formula aloud (or annotate it) so the relationships stick.
- Write each step in your own words and compare with the numbered list above.
- Swap in new numbers for the Example to make sure the calculator (and your logic) handles edge cases.
- Check at least one related calculator below — it's the fastest way to confirm your numbers still line up from a different angle.
FAQ & notes
Why is my real transformer's output voltage lower than this calculation?
This assumes an ideal, lossless transformer. Real transformers lose a few percent of output voltage to winding resistance and core losses, and that gap grows as load current increases — check the datasheet's regulation spec for a realistic figure.
Does this work for center-tapped or multi-winding transformers?
Only for a single primary-to-secondary pair. Run the calculation separately for each secondary winding, since each can have its own turns ratio relative to the primary.
What formula does the Transformer Turns Ratio Calculator use?
Voltage scales directly with the turns ratio, while current scales inversely — a step-down transformer that halves voltage doubles available current, assuming no losses.
How do I use the Transformer Turns Ratio Calculator?
Enter the primary (input side) voltage and its winding turns count. Enter the secondary (output side) turns count. Optionally enter primary current to see the corresponding secondary current an ideal transformer would deliver.