GSM and shade factor describe different properties. GSM is mass per square metre, while shade factor is an optical performance value. They may be related within one construction family, but one cannot be reliably calculated from the other without measured data.
Calculate GSM from a measured sample
Cut a representative sample, measure its dimensions without stretching, weigh it on a calibrated scale, and divide the mass in grams by the area in square metres.
Formula: GSM = sample mass (g) ÷ sample area (m²). For a 0.5 m × 0.5 m sample weighing 22 g, the area is 0.25 m² and the result is 88 GSM. Take samples across the roll and report the average and range.
Estimate theoretical roll weight
Formula: net weight (kg) = width (m) × length (m) × GSM ÷ 1,000. A 4 m × 100 m roll at 90 GSM has a theoretical net weight of 36 kg.
The shipping weight is higher because it includes the core, straps, bag, labels, and pallet. Purchase orders should distinguish net material weight, gross roll weight, and allowable tolerance.
Why GSM does not equal shade factor
Shade factor depends on yarn width, yarn shape, color, knit or weave geometry, density, stretching, and the test spectrum. A high-GSM open monofilament net can transmit more light than a lower-GSM tape construction.
Require a measured shade-factor or light-transmission report for the actual color and construction. Do not accept a conversion table based only on GSM unless it is supported by test data for that product family.
Select shade factor around the crop and climate
| Project input | Procurement question | Why it matters |
|---|---|---|
| Crop and growth stage | What light range is required? | Seedlings and mature crops differ |
| Season and latitude | What is peak solar radiation? | The same net performs differently by location |
| Inside or outside installation | Where will the net be mounted? | Cooling and wind loads change |
| Ventilation | Is the house naturally or mechanically ventilated? | Dense netting can retain heat |
| Control method | Fixed or retractable? | Repeated movement changes strength needs |
Control production and roll tolerances
- GSM average and minimum/maximum tolerance
- Measured shade factor for the quoted color
- Width and length tolerance
- Yarn construction and raw material
- UV stabilization and expected exposure
- Tensile and tear strength
- Edge reinforcement, eyelets, clips, and sewing
- Roll weight, core, labels, and export packing
Avoid common specification mistakes
Do not mix shade rate, shade coefficient, and light transmission without defining the test method. If light transmission is 35% under a stated method, the simple blocked-light percentage is approximately 65%, but commercial terminology and spectral measurements can differ.
Confirm whether percentages are nominal marketing grades or tested values. Record the instrument, standard, sample condition, and tolerance used for acceptance.
Frequently asked questions
Can shade factor be calculated directly from GSM?
No. GSM measures mass; shade factor measures optical performance. Use a test result for the exact construction and color.
How do I calculate the weight of a shade-net roll?
Multiply width by length by GSM and divide by 1,000 to obtain theoretical net kilograms.
Should a nursery choose the highest shade percentage?
No. Excess shade can reduce photosynthesis and plant quality. Match shade to crop, growth stage, season, location, and ventilation.
Send us your purchasing requirements.
Include the target specification and quantity for a more useful response.
Get a Quote