NHL products are bought by weight but mixed by volume.
Their low density in comparison with other binders means that with the same weight one would produce up to three times the amount of mortar.

Binder consumption for 1cu. yard of mortar:
volume /weight comparison

 

Average
Volumetric Mixes – lbs/cu.yd
Binder
Density (lbs/cu.yd
1:2
1:2.5
1:3
NHL 5
1123
561
448
374
NHL 3.5
1028
514
411
342
NHL 2
944
472
378
314
Lime Putty
2276
1138
910
759
OPC/W.Cement
2444
1222
978
814

Mortar required per 100 square yards of brickwork with 3/8″ joints
.
Brick sizes have been taken to be 8.5″ X 4″ X 2.5″.  Mix
ratio 1:2.5.
Type of wall
Wall
thickness

No. frog
cu. yd

Single
frog cu.yd
Amount of NHLs in lbs
(No frog/single frog)
NHL 5
NHL 3.5
NHL 2
Half brick
4 inch
1.52
2.48
674/1054
622/1020
572/937
Cavity
10 inch
3.03
4.47
1348/2210
1246/2041
1145/1876
One brick solid
8.5 inch
3.89
5.91
1730/2591
1598/2395
1469/2198
one & half brick solid
13 inch
6.25
9.16
2782/4077
2571/3767
2360/3460
St Astier NHL binders required (in lbs approx.) per 1/16″ per
square yard of render / plaster
using well graded sand # 6 down to #200(0.35of sand per sq. yd per 1/16″
of thickness).
Mix ratio
NHL 2
NHL 3.5
NHL 5
1:1.5
1.08
1.20
1.37
1:2
0.82
0.91
1.02
1:2.5
0.64
0.70
0.82
1:3
0.56
0.58
0.67