Compost maker price: UK box versus a 7 kg bundle

You are in the aisle with a 3.5 kg tub of Garotta in one hand and a phone in the other, because amazon.co.uk is showing two of those tubs for £17.99. The compost maker price on the shelf, the price per kilo, and the price of bran are three different sums. This page lines up the named shelf prices, does the division, and stops where the products stop doing the same job.

The figures are garden-centre pages and this batch's amazon.co.uk listings, captured on 15 October 2026. We compared those prices, pack sizes, and review lines, and we did not run a heap trial. A garden-centre page can change before you reach the till. A qualifying purchase through our links can earn us a commission at no extra cost to you.

In short

A single 3.5 kg Garotta box was £6.99 to £7.99 at the garden centres we checked, about £2.00 to £2.28 a kilo. The amazon.co.uk twin pack at £17.99 works out at about £2.57 a kilo, so the bundle costs more per kilo than those singles, and some reviews mention leaks. A £6.21 liquid and bokashi bran are different jobs, and the Royal Horticultural Society says a bought accelerator is usually unnecessary if the mix is already balanced.

The compost maker price of a 3.5 kg box

A Garotta 3.5kg price depends on the till. On 15 October 2026, Highway Garden Centre and Pennells showed £6.99 for 3.5 kg, Wickes showed £7.50 with delivery and click and collect, The Gardens Group showed £7.75, and Squire's Garden Centres showed £7.99. Crocus had listed £6.99 and showed the box sold out. If the shop near you is already out, use the next named price.

Per kilo those boxes are about £2.00, £2.14, £2.21, and £2.28. The dearest tub is £1 above the cheapest, about 28 pence a kilo, a thin reason to cross town when the £7.50 box is already in the car. These are the consumer prices on the page. We did not add 20 per cent, and a Wickes delivery can change the total while the tub stays at £7.50.

The pack you hold outranks the webpage, because the shop sentences disagree. Highway still leads with nitrogen and limestone, Wickes carries a weed-seed claim we did not test, and Squire's mentions chitin. Westland's page describes bacteria and fungi, a microbial feed, lime as a buffer, drainage material, and chitin, at 200–250 g on each 30 cm layer, plus about 4.5 litres of water if the waste is dry. Older copy still says 2–3 tablespoons per square metre on an 8 cm layer, and the amazon.co.uk listing prints no dose, so follow the tub you bought.

The compost maker price of a 7 kg bundle

The listing is Topline Garotta, two 3.5 kg boxes, 7 kg of powder, at £17.99. That compost maker price is £2.57 a kilo, against about £2.28 at Squire's and about £2.00 at Highway or Pennells, so the single box is the lower rate. Two singles come to £13.98, £15.00, £15.50, or £15.98. A compost maker bulk buy of the twin pack is a parcel of two tubs, about £2 more than two Squire's boxes or about £4 more than two Highway boxes.

The bundle can still be the order when the £6.99 single is sold out, as Crocus showed, or when you want one delivery. £17.99 is the 15 October 2026 capture, with 4.5 stars from 151 reviews and rank 2 in Compost Accelerators. Reviewers describe a warmer bin, and also split boxes and leaks. A burst carton goes back to the seller, and the £2.57 figure assumes the powder arrived intact. The top pick on the compost accelerator comparison is this powder for a moist, aired, leaf-heavy bay. A sealed kitchen bucket takes bran.

Sweep a spill and use only a printed dose on a heap. We make no pet-safety claim for spilled powder. The buying guide is where you choose the type before a kilo price.

Liquids, bran, and grit are different sums

BritishBasics is £6.21 for 500 ml in this batch, 4.0 from 190 reviews, with the United Kingdom listed as the origin. A search for the cheapest compost accelerator lands on that bottle inside this capture, and the live price can move. It is 500 ml of liquid beside 3.5 kg of powder, so each offer needs its own sum. UK reviews say the bottle never states neat or diluted, one buyer returned it over an unclear dose, and others report a start or no change. The £6.99 Highway box costs 78 pence more, and the maker's page prints the grams, which is what turns a cash price into a compost accelerator cost per layer.

Biorfe's 1 kg wheat bran was £12.95, origin Turkey, 4.5 from 63 reviews, with two captured reviews marked United Kingdom, so that bokashi bran price is £12.95 a kilo. Moutta's 3 kg bag was £29.99, £10 a kilo, origin France, 4.6 from 221 reviews, one captured UK review, and a dose of 1–2 tablespoons a day. Those stars are amazon.co.uk aggregates. The RHS treats bran as about a fortnight of pre-compost, then a trench or a heap, so a bran kilo and a Garotta kilo answer different jobs. The bokashi and heap page keeps that split.

Lava-Lite was £9.76 for 1 litre and £14.13 for 3 litres. The titles talk about bacteria, and the UK reviews describe pale stones and dust, so a mineral bag stays off a compost-maker shortlist.

When grass is the cheaper option

The RHS says a bought accelerator is usually unnecessary when greens, browns, and air are balanced, and that lime you add yourself brings no benefit. Grass clippings are the free nitrogen, so the price that matters is £0 where the lawn is growing and the clippings meet chopped browns. Garden Organic's rule of thumb is roughly equal volumes, and the RHS page uses about 25–50 per cent soft green and 50–75 per cent chopped brown, so pick one method. A thick slab of fresh clippings with no leaves, cardboard, or shredded stems starts the smell, and the smell wipes out a saving that began at nothing.

The limit is no lawn, a long dry spell, or a winter with the mower idle since October, and then the shelf prices above are the ones to take to the till. Leave a separate bag of garden lime in the shed, because Garotta's page already includes lime as a buffer. A cold dalek in January stays cold if the only change is a sprinkle. The how to use page is where layer depth and dose sit together, and the pack wins when it disagrees with an older webpage. A soaked bin needs browns and a week with fewer scraps, because more powder on slime leaves the slime wet.

How long a box lasts

Westland's published dose is 200–250 g on each 30 cm layer. A 3.5 kg box is 14 layers at 250 g and 17 layers at 200 g, with 100 g left at the lower dose. The 7 kg bundle is 28 or 35 layers. The sums are arithmetic from the maker's figure, not a timed trial of the Topline parcel, and the amazon.co.uk listing does not print this dose. If your tub says 2–3 tablespoons on an 8 cm layer, these counts belong to the other instruction.

One 30 cm layer every fortnight from March to October is about 16 layers. That is one small box at 200 g, and a little more than one box at 250 g. The twin pack then looks like two such seasons for one bay, or one season for two bays, only at that pace. A dalek filled once a month still holds powder next spring, and a large heap rebuilt after every mow can finish 3.5 kg before summer.

The maker's page suggests about 4.5 litres only when the waste is dry or woody. Fourteen dry layers are on the order of 60 litres, a small sum on a metered bill and a reason to pause in a drought. Skip the sprinkle on a wet bin, and keep an opened tub sealed. A leak in transit wastes the same powder if the carton then sits under a shed drip.