FPGA Resource Utilisation Calculator
Work out fpga resource utilisation instantly with clear inputs, formula shown and shareable results.
About FPGA Resource Utilisation Calculator
FPGA utilisation must be checked per resource type, because a design can be BRAM limited at 40% LUT usage. Above roughly 80% overall, routing congestion makes timing closure disproportionately harder and compile times grow sharply.
Formula
FPGA utilisation
utilisation = used / available per resource type; the highest one governs
Worked example
With the default values below, FPGA Resource Utilisation Calculator returns LUT utilisation of 70.00%. Change any input above and every figure here is recalculated in your browser.
Inputs used
- LUTs used
- 84,000 LUTs
- LUTs available
- 120,000 LUTs
- Block RAMs used
- 180 blocks
- Block RAMs available
- 240 blocks
Results
- LUT utilisation
- 70.00% %
- Block RAM utilisation
- 75.00% %
- LUTs remaining
- 36,000 LUTs
- Routability assessment
- Comfortable utilisation
Step by step
- 1Values used
- 2FPGA utilisation
- 3LUT utilisation= 70.00 %
- 4Block RAM utilisation= 75.00 %
- 5LUTs remaining= 36,000 LUTs
- 6Routability assessment= Comfortable utilisation
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why is 80% a practical ceiling?
Routing resources become the bottleneck before logic does. Congestion forces longer detours, which fails timing and lengthens place-and-route dramatically.
Which resource usually runs out first?
Block RAM or DSP slices in signal processing designs, LUTs in control-heavy designs. Always check all four including IO.
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