Knitting is precision craft at its core. A sweater worked at the wrong gauge can be two sizes off. A sock heel miscalculated by ten stitches won’t fit. A raglan yoke with incorrect shaping math produces a garment that bunches at the shoulders. The arithmetic behind knitting isn’t complicated, but it has to be exact, and doing it by hand mid-project is where most mistakes happen.
FiberTools knitting calculators use the inputs and arithmetic models stated on each page. The gauge calculator compares measured proportions and counts; it cannot prescribe an exact needle change because yarn, stitch pattern, technique, and maker tension also affect the fabric. The yarn calculator scales the measured yarn used by a representative swatch to a flat rectangular project, with an optional allowance and label-based whole-skein count. It does not estimate shaped garments or derive yarn use from gauge alone.
Construction calculators are bounded planning references, not complete patterns or fit guarantees. The raglan calculator uses the measurements shown on its page for a limited arithmetic checkpoint. It does not replace a construction-specific sweater pattern or fitting plan. Thesock calculator is a circumference-planning reference; heel, gusset, toe, and pull-on fit require a tested construction and additional measurements. The hat calculator models one explicit bottom-up, eight-section decrease schedule and does not select a universal crown method.
For finishing and project planning, the blocking calculator reports the signed percentage change between current and requested dimensions. It does not predict fabric growth or choose a treatment; compare the request with a representative swatch treated under the item's care instructions. The cast-on calculator adjusts your stitch count to the nearest stitch multiple for your chosen pattern. Every self-service calculator listed here is free. Optional professional reviews and project downloads are separate paid offers.